Eivind Ystrøm

• Sirotina, Ulyana; Bjarnadottir, Bryndis Lara; Butwicka, Agnieszka; Ystrom, Eivind; Suvisaari, Jaana & Kiviruusu, Olli [Show all 11 contributors for this article] (2026). Mental health and healthcare use during COVID‐19 among neurodivergent youth and youth with pre‐existing psychiatric disorders: A systematic review. JCPP Advances. doi: 10.1002/jcv2.70176. Full text in Research Archive Show summary

  Abstract Background Neurodivergent youth and youth with pre‐existing psychiatric disorders may have faced additional challenges in navigating the demands and restrictions of the COVID‐19 pandemic. However, less is known about how mental health outcomes and psychiatric healthcare utilization differed across diagnostic groups and other youth‐related factors. This systematic review synthesizes evidence on mental health symptoms and psychiatric healthcare use among youth with pre‐existing conditions during the pandemic. Methods We searched PubMed, Web of Science and additional sources for cross‐sectional and longitudinal studies with data collected between March 2020 and May 2023. Eligible studies included neurodivergent youth and/or youth with psychiatric disorders confirmed through clinician diagnosis or medical records prior to the pandemic. Given the clinical and methodological diversity of studies, findings were synthesized narratively. Results Forty‐eight studies met the inclusion criteria. Mental health outcomes showed mixed patterns both across and within diagnostic groups, with individual studies reporting symptom increase, stability and improvements. Evidence on psychiatric healthcare utilization was more limited and suggested different patterns between service use and psychotropic medication use. Compared to boys, girls were more likely to experience COVID‐related distress and increases in psychiatric service use during the pandemic. Age‐related findings varied across developmental stages and outcome domains. Most studies ( n  = 40; 83.3%) had a moderate overall risk of bias (RoB), while seven (14.6%) had a high overall RoB. Conclusion Mental health outcomes among youth with pre‐existing conditions during the COVID‐19 pandemic varied both within and across diagnostic groups. Outcomes were also associated with individual, developmental, contextual and service‐related factors. These findings suggest the importance of considering such factors alongside diagnosis when identifying clinical needs and planning support during large‐scale societal disruptions. Evidence on psychiatric healthcare utilization remains limited. More methodologically robust research is needed to clarify mental health and healthcare‐use patterns during major public health emergencies.

• Carson, Alexis Christine; Zidan, Mahmoud; Olstad, Emilie Willoch; Gervin, Kristina; Galesloot, Tessel E. & Scholte, Iris [Show all 9 contributors for this article] (2026). Genetically Informed Research Designs in Perinatal Pharmacoepidemiology: A Methodological Overview. Drug Safety. ISSN 0114-5916. 49(7), p. 761–773. doi: 10.1007/s40264-026-01647-9. Full text in Research Archive Show summary

  Despite the widespread use of medications during pregnancy, ethical and methodological barriers to clinical trials make observational studies necessary for evaluating medication safety in this population. Observational studies are prone to biases that often limit their validity due to the lack of randomization; integrating genetic information through discordant sibling designs, polygenic scores, and Mendelian randomization can address several confounding issues. However, application of these three approaches in perinatal pharmacoepidemiology has been limited. Complementing traditional designs with these genetically informed research designs can tackle common biases and strengthen causal inference. This paper focuses on applying genetically informed research designs to child outcomes in perinatal pharmacoepidemiology by reviewing various methods, discussing their strengths and limitations, and examining their application to date, as well as considerations for implementing them in future research. Such considerations include the availability of genetic data, the complexity of integrating genetic data with existing epidemiological data, and selection of appropriate genetic instruments for analyses. Incorporating causal inference in perinatal pharmacoepidemiology can ultimately contribute to enhancing safe medication use during pregnancy.

• Ystrom, Eivind (2026). Editorial: When children also shape the family environment. JCPP Advances. 6(2). doi: 10.1002/jcv2.70136. Full text in Research Archive Show summary

  Family research in child and adolescent mental health has often been framed as if influence runs mainly from adults to children. Bjørndal et al. provide a timely corrective. Using longitudinal network models that separate within‐person from between‐person associations, they show that adolescent mental health difficulties and family dynamics are interrelated over time, and that emotional symptoms may precede later hyperactivity/inattention and sibling problems. Their findings also point to reinforcing loops within the family system, particularly between low family support and negative feelings towards the family. This matters because family members are not merely environmental exposures; they are genetically correlated social environments, and children can shape parental and sibling dynamics as well as be shaped by them. Distinguishing between variables with stronger outgoing and ingoing influence may help refine which intervention hypotheses should be prioritized, and which should be discarded or treated more cautiously.

• Hoyos, Lucía de; Schlag, Fenja; Jahagirdar, Sanjeevan; Corfield, Elizabeth Claire; Allegrini, Andrea G. & Admiraal, Danielle [Show all 95 contributors for this article] (2026). Genome-wide analysis of social behaviour across social domains, reporters and developmental stages: a meta-regression approach. Nature Human Behaviour. doi: 10.1038/s41562-026-02551-z. Full text in Research Archive Show summary

  Social behaviour is a heritable trait linked to well-being and mental health, yet it varies across social context, including social domains, informants and development, which may shape its underlying genomic architecture. Here, we conducted a genome-wide meta-regression meta-analysis of social behaviour from infancy to early adulthood, studying ~500,000 repeated measures in European-ancestry cohorts ( N  = 73,321). We modelled heterogeneity in single-variant associations across social domains (low prosocial behaviour and peer/social difficulties), multiple informants (parents, teachers and self-reports) and ages (2–29 years), identifying 6 associated loci, including variation within CADM2 ( P  = 2.51 × 10 −9 ). Single nucleotide polymorphism-based heritability ranged from 2% to 7%, and the genetic architecture comprised 4 factors reflecting differences in either social domains or informants. Polygenic scores ( N  = 16,305) accurately predicted contextual variation in independent cohorts, with some cross-ancestry transferability. Context-specific patterns of genetic correlations, particularly when estimating the developmental onset of associations, offer opportunities to disentangle shared trajectories linking social behaviour with later-life and mental health outcomes.

• Schwaba, Ted; Sullivan, Margaret L. Clapp; Akingbuwa, Wonuola A.; Ilves, Kerli; Tanksley, Peter T. & Williams, Camille M. [Show all 138 contributors for this article] (2026). Robust inference and correlates from genetic associations with personality. Nature. ISSN 0028-0836. doi: 10.1038/s41586-026-10992-9. Full text in Research Archive
• Poornikoo, Mehdi; Fang, Yuan; Sundgot-Borgen, Christine; Klomstén, Anne Torhild; Folstad, Siri Hausland & Edvoll, Maud [Show all 12 contributors for this article] (2026). The Effect of School Resources on Student Mental Health under the Norwegian Curriculum Reform. Open Science Framework (OSF). doi: 10.17605/OSF.IO/SCA53. Full text in Research Archive
• Edvoll, Maud Clemson; Poornikoo, Mehdi; Klomstén, Anne Torhild; Sundgot-Borgen, Christine; Ystrom, Eivind & Røysamb, Espen [Show all 11 contributors for this article] (2026). OSF Embargoed Preregistrering; A Norwegian School Reform: The Effects of ‘Health and Life Skills’ for the Socioemotional School Climate. Open Science Framework (OSF). doi: https:/osf.io/tfrqu/overview. Full text in Research Archive
• Demange, Perline Aline Delle; Nivard, Michel G.; Torvik, Fartein Ask; Eilertsen, Espen Moen; Cheesman, Rosa Catherine Gillespie & Nordmo, Magnus [Show all 9 contributors for this article] (2026). No evidence of parental mental health influencing children’s academic achievement: a within-family study. European Child and Adolescent Psychiatry. ISSN 1018-8827. doi: 10.1007/s00787-026-03100-9. Full text in Research Archive Show summary

  Children of parents with psychopathology generally perform less well in school than their peers. Parental symptoms might not, however, account for their lower achievement, as other familial factors might contribute. To examine the role of parental symptoms, we analyse data from 9,000 families in the Norwegian Mother, Father, and Child Study (MoBa). Parents reported their symptoms of anxiety, depression, ADHD, eating disorders, and alcohol use disorder during pregnancy and during their child’s childhood. Children in 5th grade (aged 10) completed nationally-standardised tests of mathematics, reading comprehension, and English (as an additional language). Comparing children who are cousins (children-of-siblings design), we controlled for unmeasured factors shared among family members that confound the relationship between parental mental health and children’s academic achievement. We found small associations between greater parental symptoms and lower scores in reading and mathematics (− 0.060 ≤ β ≤ −0.013). However, these associations were no longer significant when comparing cousins whose parents differ in mental health. Results suggest that parental symptoms do not exert a direct, clinically meaningful effect on children’s academic achievement. Although non-significant, associations with parental symptoms measured close to the child’s academic test are less attenuated than those measured during pregnancy. Notably, comparison between the overall MoBa sample and the children-of-siblings samples suggests ascertainment differences that hinder strong generalisations. Our findings underscore the importance of quasi-experimental family designs in identifying modifiable targets in intergenerational health and education research. Supporting parental mental health is crucial but its direct effect on children’s achievement may be smaller than often thought.

• Bright, Joanna K.; Ahmadzadeh, Yasmin I.; Oginni, Olakunle; Viding, Essi; Leve, Leslie D. & Neiderhiser, Jenae M. [Show all 11 contributors for this article] (2026). Triangulating evidence for genetic and environmental components of associations between parental behaviours and aggressive behaviour in children. Nature Communications. 17(1). doi: 10.1038/s41467-026-75095-5. Full text in Research Archive Show summary

  Parenting behaviours are often linked to childhood aggression, but many studies fail to account for shared genetics or test directionality. Using family-based designs, we control for genetic confounding and examined bidirectional effects across two samples. First, we apply a children-of-twins/siblings design in the Norwegian Mother Father and Child Cohort Study which uses genetic relatedness between family members to separate genetic and environmental components of parent-child associations. Second, we use longitudinal models in the USA-based Early Growth and Development Study, an adoption sample where parents and child are not genetically related, enabling estimation of parent-child associations without genetic confounding. Across both studies, we find evidence for genetic and environmental transmission between parenting and child aggression. We show significant child-to-parent effects on inconsistent discipline in both samples. In the children-of-twins analysis, the association between positive parenting and child aggression is shown to be due to shared genetics, where no statistically significant association is observed in the adoption sample. These findings build on the growing body of literature showing genetic influences on both aggression and parenting behaviours, whilst underscoring the value of triangulation.

• Bond, Tom A.; McAdams, Tom A.; Warrington, Nicole Maree; Hannigan, Laurie; Eilertsen, Espen Moen & Ayorech, Ziada [Show all 12 contributors for this article] (2026). Parental body mass index and offspring childhood body size and eating behaviour: A structural equation modelling analysis in the Norwegian Mother, Father and Child Cohort Study. PLoS Medicine. ISSN 1549-1277. 23(6). doi: 10.1371/journal.pmed.1005094. Full text in Research Archive Show summary

  Background The intergenerational transmission of obesity-related traits could propagate an accelerating cycle of obesity, if parental adiposity causally influences offspring adiposity. The extent to which intergenerational obesity associations are due to such causal effects, as opposed to genetic confounding (inheritance), is unclear. We aimed to establish whether associations between parental peri-pregnancy body mass index (BMI) and offspring birth weight (BW), BMI until 8 years of age, and 8-year-old eating behaviour are due to genetic confounding. Methods and findings Data were from the Norwegian Mother, Father and Child Cohort Study, a prospective population-based birth cohort born between 1999 and 2009 at 50 out of 52 hospital maternity units in Norway. We compared the strength of the associations of maternal pre-pregnancy BMI versus paternal BMI during pregnancy, with offspring outcomes including birth weight and BMI assessed between age 6 months and 8 years of age, and appetite-related eating behaviour traits assessed at age 8 years via the Child Eating Behaviour Questionnaire (CEBQ), adjusting for potential confounders including parity, parental/grandparental language group and parental age, smoking, education and income). We then used an extended children of twins structural equation model (SEM) to quantify the extent to which associations were due to genetic confounding. Up to 85,866 children (51.3% male) were included in linear regression models, whereas SEM models included up to 50,999 children. Maternal BMI was more strongly associated than paternal BMI with offspring BW, but the maternal-paternal difference decreased for offspring BMI after birth. Greater parental BMI was associated with obesity-related offspring eating behaviours. SEM results indicated that genetic confounding did not explain the association between parental BMI and offspring BW, but explained the majority of the association with offspring BMI from 6 months onwards. For 8-year BMI, genetic confounding explained 79% (95% CI [62, 95]; p = 1.9 × 10−12) of the covariance with maternal BMI and 94% (95% CI [72, 113]; p = 2.7 × 10−14) of the covariance with paternal BMI. Limitations of this study include selective recruitment and attrition, potential bias due to parental assortative mating, and that findings may not generalise beyond high-income country settings with high obesity prevalence. Conclusions We found strong evidence that parent–child BMI associations may primarily be due to genetic confounding. When considered alongside prior evidence, this finding may argue against a strong causal effect of maternal or paternal adiposity on childhood adiposity via intrauterine or periconceptional mechanisms.

• Bjørndal, Ludvig Daae; Hegemann, Laura Elizabeth; Pettersen, Johanne Hagen; Corfield, Elizabeth Claire; Hannigan, Laurie & Yilmaz, Zeynep [Show all 14 contributors for this article] (2026). Investigating Relationships Between Genetic Risk, Childhood Maltreatment, and Eating Disorders in Women. Biological Psychiatry: Global Open Science. 6(5). doi: 10.1016/j.bpsgos.2026.100761. Full text in Research Archive Show summary

  Background Genetic and environmental factors contribute to eating disorder risk, yet their interplay is poorly understood. We examined whether childhood maltreatment and polygenic scores for anorexia nervosa (PGS-AN) and binge-eating broad (PGS-BEB) are associated with eating disorders. We also examined the interactions between childhood maltreatment and PGSs in predicting eating disorders. Methods This nested case-control study used data from up to 63,989 mothers in the MoBa (Norwegian Mother, Father and Child Cohort Study). Mothers reported on their own experiences of 4 childhood maltreatment types: long-term humiliation or degradation, threats to self or someone close, physical abuse, and sexual abuse. Diagnoses of AN, bulimia nervosa (BN), binge-eating disorder (BED), purging disorder (PD), and binge-eating spectrum disorders (BESP) were obtained using self-report data from 5 time points and population health registers. Results The prevalence of AN, BN, BED, PD, and BESP was 2.19%, 4.15%, 10.39%, 0.60%, and 12.96%, respectively. All childhood maltreatment types were strongly associated with elevated eating disorder likelihood (with odds ratios [ORs] ranging from 1.71 to 3.29) as were eating disorder PGSs (with ORs ranging from 1.05 to 1.31). There were no multiplicative interaction effects between childhood maltreatment and PGSs. Small additive interactions were observed between PGS-AN and PGS-BEB and degradation/humiliation for BN and BESP in exploratory analyses. Conclusions Eating disorder PGSs and childhood maltreatment are associated with higher odds of eating disorders. Furthermore, we found tentative evidence of small additive interaction effects between polygenic liability and childhood maltreatment, suggesting that their combined influence further elevates the risk of some eating disorders.

• Wechsler, Daniel L.; Eilertsen, Espen Moen; Ahmadzadeh, Yasmin I.; Cheesman, Rosa Catherine Gillespie; Adamo, Nicoletta & Hannigan, Laurie [Show all 8 contributors for this article] (2026). Direct and Indirect Genetic Effects on Child ADHD Traits in Early and Mid-Childhood: Trio Genome-Wide Complex Trait Analyses in a Large Norwegian Birth Registry Cohort. Behavior Genetics. ISSN 0001-8244. 56(4), p. 184–193. doi: 10.1007/s10519-026-10273-1. Full text in Research Archive Show summary

  Genetic variants in family members may exert environmentally mediated indirect genetic effects on children’s attention-deficit hyperactivity disorder (ADHD) traits. We set out to quantify the indirect genetic effects of parents’ genotypes on children’s ADHD traits as measured in early and mid-childhood. We analyzed data from genotyped trios of children, mothers, and fathers of European ancestry from the Norwegian Mother, Father and Child Cohort Study (MoBa) birth cohort. Child ADHD data were available for analytic subsamples of 12,374 trios at age 5 (children 50.5% male), and 12,714 trios at age 8 (children 50.9% male). We quantified direct genetic effects of children’s genotype and indirect effects of mothers’ and fathers’ genotypes on children’s ADHD traits at each age. Differing patterns of direct and indirect genetic effects were observed in early and mid-childhood, with predominantly maternal indirect genetic effects on ADHD traits at age 5, and roughly equal direct genetic effects and maternal indirect effects on ADHD traits at age 8. However, large standard errors hindered confident inference as to the relative importance of specific effects, and model fit comparisons ultimately favored models with no indirect genetic effects at age 5 and 8, as well as no direct genetic effects at age 5. We do not find clear evidence of indirect genetic effects of maternal or paternal genotype on child ADHD traits at ages 5 and 8, nor direct genetic effects on child ADHD traits at age 5. While previous findings of indirect genetic effects on ADHD subdomains at ages 3 and 8 broadly support the plausibility of indirect genetic effects operating on total ADHD scores at ages 5 and 8, it appears that indirect genetic effects on overall ADHD trait magnitude may be more difficult to estimate with precision than subdomain-specific effects.

• Porneso, Ralph; Havdahl, Alexandra; Eilertsen, Espen Moen & Ystrom, Eivind (2026). Longitudinal genome-wide analysis reveals putative non-additive loci in trait development. Cell reports. 45(8). doi: 10.1016/j.celrep.2026.117840. Full text in Research Archive Show summary

  Complex traits emerge from reciprocal interactions among genotype, environment, and developmental processes. Yet, standard genetic models assume purely additive effects, potentially obscuring non-additive effects. Here, we introduce a longitudinal log-linear variance and genotype-by-time model to detect associations from within-individual variation departing from additivity, i.e., putative non-additive effects. Applied to early growth (infant length and BMI) and cognitive traits (math and reading) of 45,000 to 65,000 individuals, we report 76 lead putative non-additive loci that are enriched 16-fold for cis-regulatory interactions. Of the 76, 6 overlap prior interaction studies (anthropometric) and only 3 loci overlap prior genome-wide association study (GWAS) (cognitive). Accounting for scale effects and linkage disequilibrium (LD), we observe that additive effects are correlated with putative non-additive effects, i.e., “effect pleiotropy.” These results are consistent with non-additive genetic contribution to trait development, which may partly be absorbed by effects estimated under standard GWAS parameterization that assumes strict additivity.

• Rayner, Christopher; Hannigan, Laurie; Badini, Isabella; Demange, Perline Aline Delle; Ofstad, Sverre Berg & Ystrøm, Eivind [Show all 7 contributors for this article] (2026). Quantifying and adjusting for selection biases in the Norwegian Mother, Father and Child Cohort Study using population-wide individual-level registry information. International Journal of Epidemiology. ISSN 0300-5771. 55(4). doi: 10.1093/ije/dyag122. Full text in Research Archive Show summary

  Background Selective participation in research studies hampers researchers’ ability to draw valid and generalizable inferences from analyses. Quantifying and adjusting for selective participation are desirable but can be challenging given the paucity of data for non-participants. Methods We used individual-level information from population registers to predict baseline and continued participation in the Norwegian Mother, Father and Child Cohort Study (MoBa). Inverse probability weights were computed from logistic regression models with elastic-net regularization. We predicted selective participation and attrition in 296 987 mothers, of whom 29% returned the first MoBa questionnaire and 12.5% returned a follow-up questionnaire 8 years later. To quantify bias, we computed sample characteristics and exposure–outcome associations in the target population and stratified samples. To compare approaches for adjusting for bias, we computed weighted sample estimates by using three sets of weights. Results Unweighted sample estimates were systematically different from target-population values, indicating bias due to selective participation. Baseline participation weights substantially reduced the impact of selection bias on mean values by 93% and associations by 75%. Attrition weights reduced attrition bias on mean values by 78% and associations by 50% but were less effective for reducing participation bias (22% and 14% respectively). Conclusion In this sample, characteristics and effect estimates are substantially different from target-population values. Participation weights were relatively effective at reducing bias due to selective participation but attrition weights were not. Estimates from studies that use attrition weights may still contain non-negligible selection bias—particularly if the baseline sample is not representative of the target population. Future studies should prioritize opportunities for deriving sampling weights for participation as well as attrition.

• Krätschmer, Ilse; Hegemann, Laura Elizabeth; Hofmeister, Robin J.; Corfield, Elizabeth Claire; Mahmoudi, Mahdi & Delaneau, Olivier [Show all 14 contributors for this article] (2026). Separating direct, indirect, and parent-of-origin genetic effects in the human population. Cell Genomics. 6(7). doi: 10.1016/j.xgen.2026.101277. Full text in Research Archive Show summary

  We introduce JODIE, a genetic joint modeling approach that estimates how DNA loci influence human traits by partitioning genetic effects into four components: direct effects (from a child’s alleles), indirect maternal and paternal effects (from parents’ alleles), and parent-of-origin (PofO) effects (dependent on parental transmission of alleles), while uniquely accounting for assortative mating. We analyze 30,000 child-mother-father trios from the Estonian Biobank and the Norwegian Mother, Father, and Child Cohort, focusing on height, body mass index, and childhood educational test scores. We find direct effects to be the largest contributor to trait variation, but combined, indirect parental and PofO effects are similarly substantial. We support our results by within-family genome-wide association testing and identify 276 independently associated DNA regions with a complex interplay between direct, indirect, and PofO effects. By joint modeling, we show that direct, indirect, and PofO effects collectively shape human phenotypic variation across loci genome-wide.

• Edvoll, Maud Clemson; Folstad, Siri Hausland; Eftedal, Nikolai Haahjem; Poornikoo, Mehdi; Fang, Yuan & Ystrøm, Eivind [Show all 11 contributors for this article] (2026). A Norwegian curriculum reform: Effects for 10th graders’ academic performance. Studies in Educational Evaluation. ISSN 0191-491X. 89. doi: 10.1016/j.stueduc.2026.101616. Full text in Research Archive
• Widding-Havnerås, Tarjei; Demange, Perline Aline Delle; Zachrisson, Henrik Daae; Borgen, Nicolai; Ystrøm, Eivind & Elwert, Felix (2026). Estimating returns to education using the genetic lottery. Proceedings of the National Academy of Sciences of the United States of America (PNAS). ISSN 0027-8424. 123(15), p. 1–10. doi: 10.1073/pnas.2537049123. Full text in Research Archive Show summary

  Does more schooling cause higher lifetime earnings? Social scientists have long sought to determine the economic returns to schooling given its importance to individual life chances and public policy. Prior estimates are limited by unobserved confounding in observational studies and the focus of popular quasi-experimental studies on increases in schooling at only one particular age. Genotyped data offer an opportunity to address unobserved confounding and to estimate the returns to an additional year of schooling at any age by using quasi-randomly assigned genetic variants related to education as instrumental variables [Mendelian randomization (MR)]. We analyze comprehensive Norwegian population registries with career-long earnings data and genotyped data from the Norwegian Mother, Father and Child Cohort Study (MoBa). We employ three identification strategies for triangulation: ordinary least squares (OLS) with covariate-adjustment, sibling and twin fixed-effects models, and MR. Estimated returns to schooling are 8.0% in MR (N = 109,800) and 6.3% in sibling-MR (N = 18,666). Extensive sensitivity analyses suggest that MR results are robust even to large potential violations of MR assumptions, including pleiotropy. MR estimates somewhat higher returns than OLS for the full population (5.9%, N = 1,255,604) and fixed-effects models for siblings (5.3%, N = 966,976) or monozygotic twins (3.2%, N = 2,630). The estimated internal rate of return to schooling exceeds opportunity costs of education as proxied by the market interest rate. The lifetime returns to schooling are positive and substantial across all models.

• Chegeni, Razieh; Nes, Ragnhild Bang; Cheesman, Rosa Catherine Gillespie; Ayorech, Ziada; Ystrøm, Eivind & Røysamb, Espen (2026). Direct and indirect parental genetic effects on offspring susceptibility to internalizing problems across development. Nature Mental Health. 4, p. 754–765. doi: 10.1038/s44220-026-00619-3. Full text in Research Archive Show summary

  Internalizing problems, including symptoms of anxiety and depression, are common in childhood and adolescence and are linked to adverse long-term outcomes. Although both child genetic variants and parental genetic influences contribute to these problems, the specific direct (child) and indirect (parental) genetic pathways involved remain unclear. We applied multi-polygenic score models using elastic net regression to identify key genetic predictors of depressive and anxiety symptoms at ages 8 and 14 in 9,314 parent–child trios from the Norwegian Mother, Father and Child Cohort Study. We included 90 polygenic scores (PGSs) for the trio, along with their respective interaction terms. Predictive accuracy improved with age, with models explaining up to 2.7% of the variance in depression and 1.2% in anxiety. Key predictors included child attention deficit hyperactivity disorder, cognitive skills and well-being spectrum PGSs; maternal PGSs for smoking and cognitive skills; and paternal well-being spectrum PGSs. These findings underscore the value of incorporating diverse parental genetic traits to understand intergenerational risk transmission and developmental changes in child mental health.

• Pettersen, Johanne Hagen; Eilertsen, Espen Moen; Hegemann, Laura Elizabeth; Hannigan, Laurie; Lund, Ingunn Olea & Johannessen, Pia Myklebust [Show all 12 contributors for this article] (2026). Intra-familial dynamics of mental distress during the Covid-19 lockdown. Translational Psychiatry. 16(1), p. 1–9. doi: 10.1038/s41398-026-03876-z. Full text in Research Archive Show summary

  Lockdowns and social restrictions imposed in response to the Covid-19 pandemic intensified the proximity and reciprocal exposure among members of nuclear families. It is unclear how variation in mental distress during this period is attributed to potential influences of family members. This study used genetic data from adolescents (n = 4 388), mothers (n = 27 852) and fathers (n = 25 953), to disentangle the contributions of parent-driven, child-driven, and partner-driven components to mental distress during the first two months of the Covid-19 lockdown. Separate models also included adolescents’ non-pandemic mental distress as outcomes (n = 13 484). Trio genome-wide complex trait analyses separated two types of genetic components; direct–how an individual’s genotype is associated with their own mental distress, and indirect–how an individual’s genotype is associated with the mental distress of family members. A trio polygenic score (PGS) design was used to investigate associations of specific genetic liability factors with mental distress, and whether these changed over time (PGS×time). Results suggest that family-level genetic factors contribute to mental distress; variance components capturing indirect genetic effects accounted for 10% of adolescent mental distress (mother-driven), 2–3% of maternal (partner-driven), and 5% of paternal mental distress (child-driven). Mothers’ depression and ADHD PGS were positively associated with fathers’ mental distress. No PGS×time interactions were found. Direct genetic effects accounted for 9–10% variance in mental distress across family members, partly explained by genetic variants associated with anxiety, depression, ADHD and neuroticism. These findings highlight the importance of family dynamics and emphasize the potential value of including family members in mental health interventions.

• Qin, Qi; Cheesman, Rosa Catherine Gillespie; Eilertsen, Espen Moen & Ystrom, Eivind (2026). Children's psychological traits and educational performance: How schools and residential areas moderate how individual traits translate into academic outcomes. JCPP Advances. p. 1–15. doi: 10.1002/jcv2.70100. Full text in Research Archive Show summary

  Abstract Background The extent to which children's psychological traits influence their educational performance is thought to depend on the fit between the individual and their developmental context. However, this assumption has yet to be empirically tested on a population scale. This study examines how neurodevelopmental, mental health, and personality traits interact with latent environmental contexts to enhance, maintain, or mitigate their educational performance. Methods Using the Norwegian Mother, Father and Child Cohort Study (MoBa), we estimated the association between 16 developmental traits and grade point average (GPA) in 26,875 children across environmental contexts in 2131 primary schools, 1075 middle schools, ~14,000 neighborhoods, 1471 districts, and 347 municipalities. Results Across the developmental traits, the effect on GPA ranged from −0.286 to 0.220. However, these effects varied substantially across environmental contexts (SD 0.022 to 0.090). Trait‐by‐context interactions were detected in primary schools (2 traits), middle schools (6 traits), neigbourhoods (0 traits), districts (3 traits), and municipalities (1 trait), respectively. Moderation magnitudes were largest for neurodevelopmental traits in primary schools. On average, the effects of ADHD and communication difficulties were −0.252 and −0.193. However, these effects differed substantially across primary schools with SD 0.090 and 0.070, implying b  < −0.370 and b  < −0.282 in 10% of schools. For average children, primary schools explained 0.504% of middle school GPA. Similarly, the effect of depression and extraversion was dependent on middle‐school environments ( b  = −0.128; SD = 0.058 and b  = 0.024; SD = 0.022). Moreover, schools and districts with high GPAs tended to express lower detrimental effects on children's developmental traits. Conclusion Schools and residential areas function as educational catalysts, enhancing or mitigating the influence of developmental traits. High‐performing environments compensate for psychological challenges, whereas lower‐performing contexts exacerbate difficulties. Because the study integrated multiple traits and contextual levels, the analyses were exploratory and data‐driven, and the findings should be interpreted as hypothesis‐generating. These results suggest a need for both context‐sensitive and individually tailored educational interventions.

• Valstad, Mathias; Eilertsen, Espen Moen; Ayorech, Ziada; Cheesman, Rosa Catherine Gillespie; Demange, Perline Aline Delle & Eftedal, Nikolai Haahjem [Show all 8 contributors for this article] (2026). Indirect genetic effects of siblings. Journal of Child Psychology and Psychiatry. ISSN 0021-9630. doi: 10.1111/jcpp.70130. Full text in Research Archive Show summary

  Background Within-family designs are increasingly used to decompose genotype–trait associations into direct and indirect genetic effects. Many such designs, including trio designs or within-sibship designs, assume an absence of sibling indirect genetic effects. Methods We expand two well-known molecular genetic within-family designs, one variance component (genome-based restricted maximum likelihood) and one trait-based (structural equation modeling with polygenic indices), to estimate sibling indirect genetic effects, along with direct genetic effects. We link the Norwegian Mother, Father, and Child Cohort Study (MoBa) to Norway's national education database to model genetic effects on national standardized testing results at ages 10, 13, and 14, and on parent-rated attention-deficit hyperactivity disorder (ADHD) symptoms at ages 3 and 8 in up to 15,971 genotyped and phenotyped siblings. Results Estimates of direct and indirect genetic effects from the genome-based restricted maximum likelihood and the structural equation modeling with polygenic indices approaches converge, albeit with the variance component estimates typically an order of magnitude greater than the trait-based estimates. We observe no indirect genetic effects of siblings on educational performance at any age, and only slightly negative indirect genetic effects of siblings on ADHD symptoms at age 3. We argue that the latter effect might reflect parental contrasting ratings. Conclusions The results suggest that within-family models of educational performance are unlikely to be drastically biased by an assumption of absent sibling indirect genetic effects. Combining trait-based analyses with variance component analyses can benefit understanding of indirect genetic effects, especially when the effects are not specific to a particular mechanism.

• Valstad, Mathias; Eftedal, Nikolai Haahjem; Yang, Tianfang; Kvarstein, Elfrida Hartveit; Reichborn-Kjennerud, Ted & Ystrom, Eivind [Show all 7 contributors for this article] (2026). The epidemiology of personality disorders in Norway: a nationwide patient registry study. Social Psychiatry and Psychiatric Epidemiology. ISSN 0933-7954. doi: 10.1007/s00127-026-03083-7. Full text in Research Archive
• Eilertsen, Espen Moen; Eftedal, Nikolai Haahjem; Cheesman, Rosa Catherine Gillespie; Ayorech, Ziada; Ebeltoft, Joakim Coleman & Sunde, Hans Fredrik [Show all 9 contributors for this article] (2026). Multivariate maternal effects across the internalizing–externalizing spectrum in childhood: results from the Norwegian mother, father, and child cohort study. Journal of Child Psychology and Psychiatry. ISSN 0021-9630. p. 1–13. doi: 10.1111/jcpp.70111. Full text in Research Archive Show summary

  Background From a functionalist perspective, parenting behaviors have adaptive functions and are partly expressions of genetic variation. Maternal genes that have effects on children are often referred to as indirect maternal genetic effects. Indirect genetic effects provide a means for measuring the role of parenting without the need for specifying the relevant parental behaviors. We studied indirect maternal genetic effects to address both the importance and commonality of parenting across the internalizing–externalizing spectrum of behavior problems in childhood. We further addressed how indirect genetic effects impact our understanding of direct genetic effects if not accounted for. Methods Utilizing data from the Norwegian Mother, Father, and Child Cohort Study (MoBa), our analyses involved 42,423 children and their mothers. Both pedigree and genotype data were used to infer genetic relationships. We applied multivariate latent variable models to distinguish indirect maternal genetic effects and direct offspring genetic effects on seven measures of internalizing–externalizing behaviors. Results Our findings indicate significant maternal genetic influences, explaining 7%–18% of the variance across internalizing–externalizing behaviors. A general maternal effect common across behaviors could adequately account for most of the variability. The analyses further indicate that direct child genetic effects appear smaller and more complex when indirect maternal genetic effects are modeled simultaneously. Conclusions By summarizing the effects of parenting with indirect maternal genetic effects, we show a substantial contribution of parents with respect to internalizing–externalizing behaviors in childhood. Although parenting is multifaceted, the effects of parenting are general and can succinctly be described as a single common dimension. Further, our study demonstrates that direct genetic effects appear smaller and more complex when maternal genetic effects are accounted for, highlighting the confounding potential of parental effects in understanding the role of genetic differences in child psychopathology.

• Severinsen, Yvonne; Ystrom, Eivind; Eftedal, Nikolai Haahjem; Nygaard, Egil; Bekkhus, Mona & Viana, Karine Porpino [Show all 9 contributors for this article] (2026). Determinants of Parental Emotion Socialization Behaviors: Insights From a Large‐Scale Population‐Based Family Study. Scandinavian Journal of Psychology. ISSN 0036-5564. 67(4), p. 953–971. doi: 10.1111/sjop.70082. Full text in Research Archive Show summary

  ABSTRACT Parental emotion socialization behaviors (ESBs) are essential for child development and are typically understood as influenced by factors related to three domains: the parent, the child, and the family context. However, it remains unclear how parents' childhood experiences with ESBs should be represented within these conceptual frameworks. Addressing the complexity of ESBs, the present study examined predictors across three theoretically derived domains and additionally included parents' recollected ESBs as a parent‐level factor. Questionnaire data were collected from a large population‐based cohort of Norwegian mothers and fathers ( n  = 4207; 2460 mothers) with children aged 3 to 13 years ( M  = 7.4 years). Supportive and non‐supportive ESBs were examined separately through hierarchical regression models incorporating parent, context, and child factors. The three domains collectively accounted for 28% of the variance in supportive ESBs and 29% in non‐supportive ESBs. The results clearly emphasized parental factors, with parent gender and recollected ESBs being the most influential predictors. Other parent factors, such as perceived parenting stress, alcohol use, and the personality traits agreeableness and openness, also showed unique effects across both types of ESBs. Among contextual factors, education, income, and country of birth predicted non‐supportive ESBs but not supportive ESBs. Child age and birth order were linked with supportive ESBs, whereas only child age predicted non‐supportive ESBs. Findings highlight the importance of parent characteristics, particularly gender and recollected emotion socialization from the family of origin, in predicting current parental ESBs beyond contextual and child‐related factors.

• Ebeltoft, Joakim Coleman; Ystrøm, Eivind; Ayorech, Ziada & Eilertsen, Espen Moen (2026). Parental wealth and mental disorders in Norway (2006–2023): a nationwide registry-based study of 1.4 million young people. The Lancet Regional Health - Europe. 62. doi: 10.1016/j.lanepe.2025.101567. Full text in Research Archive Show summary

  Background Young people from families with low socioeconomic position have higher rates of mental disorders. However, wealth is underexamined despite large wealth inequity worldwide. Here, we aim to investigate the relationship between early life parental wealth and mental disorders in young Norwegians. Methods We conducted a population study of associations between early-life parental wealth and 17 diagnostic categories of mental disorders in 1.4 M children (7–12), adolescents (13–18), and young adults (19–24) observed 2006–2023. Ranked parental socioeconomic indicators at age 0–6 (wealth, income, occupation, and education) and mental disorder diagnoses (ICD-10 and ICPC-2) were obtained from Norwegian Tax, Employment, Education, and Control and Payment of Health Reimbursements registries. Estimates were derived from mean prevalences, generalised estimating equations, and sibling comparison designs. Findings Parental wealth represents a gradient in young people’s mental disorders across age, sex, diagnostic categories, and cohorts. The lowest wealth quintile demonstrated 87% [95% CI = 78–96%] higher 1-year prevalence than the highest quintile. In multivariable analyses, parental wealth was the strongest predictor of mental disorders relative risk in adolescents (1.83 [1.76–1.9]) and young adults (1.92 [1.8–2.04]), while wealth (1.53 [1.46–1.6]) and education (1.52 [1.45–1.6]) were the strongest predictors in children. Parental wealth has a significant within-family association with mental disorders (relative risks: children 1.57 [1.44–1.71], adolescents 1.34 [1.26–1.42], young adults 1.42 [1.31–1.54]). Interpretation Our study serves as a point of reference for understanding the relationship between parental wealth and mental health. Our findings establish early life parental wealth as a fundamental social gradient in young people’s mental disorders.

• Chegeni, Razieh; Nes, Ragnhild Bang; Cheesman, Rosa Catherine Gillespie; Ayorech, Ziada Ng'ombo Laurel; Ystrøm, Eivind & Røysamb, Espen (2026). Parental direct and indirect genetic effects on offsprings’ internalizing problems across development. Nature Mental Health. doi: https:/www.researchsquare.com/article/rs-6862539/v1. Full text in Research Archive Show summary

  Internalizing problems are common in youth and linked to adverse long-term outcomes. While both children’s own genetic variants (direct genetic effects) and the genetics of their parents (indirect genetic effects) contribute, the direct and indirect genetic traits involved remain unclear. Here, w...

• Tamnes, Christian K.; Bekkhus, Mona; Eilertsen, Maja; Nes, Ragnhild Bang; Prydz, Monica Beer & Ystrom, Eivind [Show all 63 contributors for this article] (2025). The nature of the relation between mental well-being and ill-being. Nature Human Behaviour. 9(12), p. 2431–2440. doi: 10.1038/s41562-025-02319-x. Full text in Research Archive
• Krogsrud, Stine Kleppe; Nordeng, Hedvig Marie Egeland; Roe, James Michael; Torkildsen, Janne von Koss; Wood, Mollie Elizabeth & Ystrøm, Eivind (2025). Associations between prenatal paracetamol exposure and brain development from ages 4–16: A longitudinal MRI study. Developmental Cognitive Neuroscience. ISSN 1878-9293. 78. doi: 10.1016/j.dcn.2025.101667. Full text in Research Archive Show summary

  Research has raised concerns regarding the potential impact of prenatal paracetamol exposure on fetal neurodevelopment. This is the first longitudinal study to investigate whether such exposure is related to structural brain development and cognitive abilities during childhood and adolescence. The sample includes 447 children aged 4.1–16.2 years with 905 MRI scans. The study is based on The Norwegian Mother, Father and Child Study (MoBa), and uses data from the Medical Birth Registry of Norway. The exposure variable is mothers’ self-reported use of paracetamol from prenatal and postnatal questionnaires. Among 447 children (229 girls; mean age 8.38 years), 193 (43.2 %) were prenatally exposed. Days of exposure range from 1 to 128 (mean 8.2). Vertex-wise linear mixed effect models showed that exposed children (n = 193; 393 scans) had slightly smaller cortical surface area and volume in some regions compared to non-exposed children. These results were seemingly driven by long-term exposed children (≥14 days in utero; n = 35; 72 scans, and exposed in all three trimesters, n = 21; 44 scans). However, group differences in brain structure were small with largely overlapping distributions, and the observational design and risk of unmeasured confounding preclude causal inference. Thus, the clinical significance remains uncertain. For cognitive abilities, results were reassuring showing no significant effect of prenatal paracetamol exposure on working memory capacity or IQ scores.

• Zugic, Milica; Trinh, Nhung; Rostami, Sina; Nordeng, Hedvig Marie Egeland; Ystrøm, Eivind & Bulik, Cynthia M [Show all 10 contributors for this article] (2025). Antenatal depressive and anxiety symptoms in women with eating disorders who continue or discontinue antidepressant treatment in pregnancy. Journal of Affective Disorders Reports. 22, p. 1–10. doi: 10.1016/j.jadr.2025.100985. Full text in Research Archive Show summary

  Background Limited evidence on antidepressant effectiveness in pregnant women with eating disorders (ED) challenges pharmacotherapy management. We examined antenatal depressive and anxiety symptoms with continued antidepressant use in women with ED. Methods We used data from the Norwegian Mother, Father and Child Cohort Study (MoBa) linked to the Medical Birth Registry of Norway and MoBa Genetics. MoBa questionnaires at weeks 17 (early) and 30 (mid-late pregnancy) measured antidepressant exposure and symptoms of depression and anxiety using the 5-item Hopkins Symptom Checklist. We fitted generalised linear models and adjusted for confounding. In a subsample, we stratified analyses by polygenic-score tertiles for antidepressant response. Results We identified 5920 pregnancies in women with ED, mainly binge-eating disorder (BED) (84.0 %) and bulimia nervosa (BN) (12.4 %). Of these, 48 (0.8 %) continued antidepressants into early pregnancy, 93 (1.6 %) discontinued during, and 85 (1.4 %) discontinued before pregnancy. At early pregnancy only, continued antidepressant was associated with lower severity of depressive and anxiety symptoms relative to discontinuation. Among women with BED, this was specific to lower anxiety symptoms (β:-0.43, 95 %CI:-0.84, -0.02). This association was not observed in women with BN. In women with higher antidepressant-response polygenic-score continued antidepressant was associated with lower symptom severity relative to discontinued (range of β:-0.86 to -1.35). Conclusions Continuing antidepressants in early but not mid-late pregnancy is associated with lower severity of depressive and anxiety symptoms in women with BED. The association observed in women with higher antidepressant-response polygenic-score calls for larger studies on personalized treatment in perinatal ED.

• Nguyen, Huong Thu; Ystrøm, Eivind; Gjerde, Line Cecilie & Næss, Øyvind Erik (2025). Life course socioeconomic position and the risk of cardiovascular events and all-cause mortality in a Norwegian twin study. Scientific Reports. 15. doi: 10.1038/s41598-025-16975-6. Full text in Research Archive
• Haskell, Erin; Sigmarsdottir, Berglind; Thorisdottir, Ingibjorg Eva; Valborgarson, Audun; Aparicio, Elena Bonilla & Kiviruusu, Olli [Show all 15 contributors for this article] (2025). Adolescent mental health before, during, and after the COVID-19 pandemic in Iceland: a repeated, cross-sectional, population-based study. The Lancet Regional Health - Europe. 53. doi: 10.1016/j.lanepe.2025.101301. Full text in Research Archive Show summary

  Background Adolescents' mental health declined during the COVID-19 pandemic, yet little is known about the long-term outcomes after the pandemic's declassification as a global health emergency (5 May 2023). This study examined changes in adolescent mental health in Iceland from 2016 to 2023, using a bioecological framework to identify risk and protective factors. Methods Youth in Iceland surveys were administered nationwide to 13-15-year-olds in 2016, 2018, 2020, 2021, 2022 and 2023, with an average 75% response rate across the years. The surveys included measures on depressive symptoms, anxiety and hostility (Symptom Checklist-90), parental social support (Perceived Parental Support Scale), screen time, and stress/trauma exposure (Negative Life Events Scale). Stepwise-reduced mixed-effects models assessed the association of age, gender, time and risk/protective factors and their effect on mental health. Multiple imputation addressed missing data, and Bonferroni corrections adjusted for multiple testing. Findings 62,011 adolescents participated: 48.2% female (n = 29,890), 50.0% male (n = 31,002), 1.8% non-binary (n = 1119). Depressive symptoms showed signs of improvement post-pandemic (2023) compared to 2021 (β 0.19, 95% CI 0.13–0.24), yet remained higher than pre-pandemic levels (2016: β −0.38, 95% CI −0.44 to −0.33; 2018: β −0.26, 95% CI −0.31 to −0.20). Anxiety and hostility also increased and remained higher than pre-pandemic levels in 2023 (anxiety: 2016 β −0.29, 95% CI −0.35 to −0.24, 2018 β −0.20, 95% CI −0.26 to −0.15; hostility: 2016 β −0.26, 95% CI −0.31 to −0.20, 2018 β −0.12, 95% CI −0.18 to −0.07). Across all the models examining the predictors from diverse bioecological spheres, low parental social support, high social media use, and bad grades were consistently associated with poor mental health, regardless of mental health outcome and gender. Interpretation The COVID-19 pandemic has had a serious and continuing negative effect on adolescents’ mental health. Targeted interventions are needed to address the increase in mental health problems during the COVID-19 pandemic, with a focus on enhancing parental support and managing screen use.

• Ebeltoft, Joakim Coleman; Eilertsen, Espen Moen; Cheesman, Rosa Catherine Gillespie; Ayorech, Ziada; Hootegem, Arno Van & Lyngstad, Torkild Hovde [Show all 7 contributors for this article] (2025). The genetic and environmental composition of socioeconomic status in Norway. Nature Communications. 16(1). doi: 10.1038/s41467-025-58961-6. Full text in Research Archive Show summary

  Estimating the contributions of genetic and environmental factors is key to understanding differences in socioeconomic status (SES). However, the heritability of SES varies by measure, method, and context. Here, we estimate genetic and environmental sources of variance and commonality in the ‘big four’ SES indicators. We use high-quality administrative data on educational attainment, occupational prestige, income, and wealth, and employ four family-based and unrelated genotype-based heritability methods, all drawn from the same population-wide cohort of >170,000 Norwegians aged 35-45. By drawing subsamples from a consistent sample and using registry-based data, we reduce differences in estimates due to population characteristics and measurement error. Our results show that genetic variation consistently explains more for educational attainment and occupational prestige. Family-shared environmental contributions explained more for educational attainment and wealth. Our results highlight considerable common influences on the four SES indicators among genetic and shared environmental factors, but not among non-shared environmental factors. Overall, we show how the relative importance of genetic and environmental factors to SES differences in Norway varies by method and type of socioeconomic attainment. This study is a reliable source for comparing heritability methods, and for comparing SES indicators and their genetic and environmental commonality in a social-democratic welfare state.

• Cheesman, Rosa Catherine Gillespie; Anapaz, Ville; Alten, Sjoerd van; Abdellaoui, Abdel; Porneso, Ralph Pascual Ortiz & Ebeltoft, Joakim Coleman [Show all 16 contributors for this article] (2025). Genetic associations with educational fields. Nature Genetics. ISSN 1061-4036. 57, p. 2997–3006. doi: 10.1038/s41588-025-02391-z. Full text in Research Archive Show summary

  Educational field choices shape careers, wellbeing and the societal skill distribution, yet genetic influences on what people study remain poorly understood. Here we show that genetic factors are associated with educational field specializations using genome-wide association studies (GWASs) across 463,134 individuals from Finland, Norway and the Netherlands (effective n between 40,072 and 317,209). We identified 17 independent genome-wide significant variants linked to 7 of 10 educational fields, with average heritability of 7%. The genetic signal is specific to field choice rather than educational level, persisting after controlling for years of schooling and confounding factors. By examining genetic clustering across specializations, we uncovered two key dimensions: technical versus social and practical versus abstract. We performed GWASs of these components and demonstrated distinct genetic correlations with personality, behavior and socioeconomic status. Our findings demonstrate that genomic research can illuminate ‘horizontal’ stratification, revealing insights into vocational interests and social sorting beyond traditional attainment measures.

• Eftedal, Nikolai Haahjem; Eilertsen, Espen Moen; Sunde, Hans Fredrik; Kleppestø, Thomas Haarklau; Ystrøm, Eivind & Czajkowski, Nikolai Olavi (2025). Beyond additive genetic effects: Explaining family resemblance in school performance across millions of pairs of Norwegian relatives. Proceedings of the National Academy of Sciences of the United States of America (PNAS). ISSN 0027-8424. 122(25), p. 1–9. doi: 10.1073/pnas.2419627122. Full text in Research Archive Show summary

  We investigate the hypothesis that family resemblance on school performance can be fully explained by additive genetic effects and assortative mating. Our sample consists of all schoolchildren who took Norwegian national standardized tests between 2007 and 2019 (N = 936,708). These tests measure aptitude in math and reading comprehension, and are taken the years children turn 10, 13, and 14 y old. We identify millions of pairs of relatives within our sample (82 different kinds, in total), including not only conventional biological relatives such as siblings and cousins, but also relatives-in-law, relatives through adoption, twins, and relatives connected through twins. When fitting models which assume that family resemblance arises solely from additive genetic effects and assortative mating, we find that they describe much of our data well, but that they systematically underestimate the similarity of close relatives (particularly monozygotic twins), maternal relatives, relatives-in-law, and relatives through adoption. We discuss potential explanations for these deviations, including shared-environmental effects, nonadditive genetic effects, and gene–environment interplay.

• Lund, Ingunn Olea; Hannigan, Laurie; Ask, Helga; Askelund, Jo Adrian Dahl; Hegemann, Laura Elizabeth & Corfield, Elizabeth Claire [Show all 12 contributors for this article] (2025). Prenatal maternal stress: triangulating evidence for intrauterine exposure effects on birth and early childhood outcomes across multiple approaches. BMC Medicine. 23, p. 1–17. doi: 10.1186/s12916-024-03834-w. Full text in Research Archive Show summary

  Background Maternal stress during pregnancy may impact offspring development via changes in the intrauterine environment. However, genetic and environmental factors shared between mothers and children might skew our understanding of this pathway. This study assesses whether prenatal maternal stress has causal links to offspring outcomes: birthweight, gestational age, or emotional and behavioral difficulties, triangulating across methods that account for various measured and unmeasured confounders. Methods We used data from the Norwegian Mother, Father, and Child Cohort Study (MoBa), including maternal reports on prenatal stress at work, at home, and via stressful life events as exposures. Outcomes were children’s birthweight and gestational age, from the Medical Birth Registry of Norway, and maternal reports on early offspring emotional and behavioral difficulties. We assessed associations using four approaches: sibling control analyses, gene-environment interaction analyses, intergenerational Mendelian randomization (MR), and negative control (i.e., postnatal stress) analyses. Results Maternal prenatal stress was observationally associated with offspring lower birthweight (e.g., βwork = − 0.01 [95%CI: − 0.02, − 0.01]), earlier birth (e.g., βwork = − 0.04 [95%CI: − 0.04, − 0.03])), and more emotional (e.g., βevents = 0.08 [95%CI: 0.07, 0.09]) and behavioral difficulties (e.g., βrelationship = 0.08 [95%CI: 0.07, 0.09]) in the full sample (N = 112,784). However, sibling control analyses (N = 36,511) revealed substantial attenuation of all associations after accounting for familial factors. Gene-environment interaction models (N = 76,288) showed no clear evidence of moderation of associations by mothers’ polygenic scores for traits linked to stress sensitivity. Intergenerational MR analyses (N = 29,288) showed no clear evidence of causal effects of maternal plasma cortisol on any offspring outcomes. Negative control exposure analyses revealed similar effect sizes whether exposures were measured prenatally or postnatally. Conclusions Our results indicate that links between prenatal maternal stress and variation in early offspring outcomes are more likely to be confounded than causal. While no observational study can rule out causality, the consistency of our findings across different approaches is striking. Other sources of prenatal stress or more extreme levels may represent intrauterine causal risk factors for offspring development. Nonetheless, our research contributes to identifying boundary conditions of the fetal programming and developmental origins of health and disease hypotheses, which may not be as universal as sometimes assumed.

• Edvoll, Maud Clemson; Folstad, Siri Hausland; Fang, Yuan; Bjørnebekk, Gunnar; Ystrom, Eivind & Eftedal, Nikolai Haahjem [Show all 10 contributors for this article] (2024). OSF preregistration: A Norwegian School Reform: The Effects of a National Curricular Change on Children’s Academic Performance. Open Science Framework (OSF). doi: https:/osf.io/e4m8c/overview?view_only=f20402d677fe4e798c1480ba6049edca. Full text in Research Archive
• Tamnes, Christian K.; Bekkhus, Mona; Eilertsen, Maja; Nes, Ragnhild B.; Prydz, Monica Beer & Ystrom, Eivind [Show all 63 contributors for this article] (2024). The nature of the relation between mental illbeing and wellbeing. Nature Human Behaviour. 9, p. 2431–2440. doi: 10.31234/osf.io/9jk2x. Full text in Research Archive Show summary

  Research on mental health has traditionally separated the study of illbeing—disorder and problems—and wellbeing—life satisfaction and positive affect. While previous reviews of studies primarily employing self-report scales indicate that illbeing and wellbeing are distinct yet interconnected constructs, a deeper examination of their relationship is lacking. This perspective article from the PROMENTA Research Center offers a review and synthesis of findings on the joint and distinct nature of illbeing and wellbeing across multiple levels of analysis. Adopting an interdisciplinary approach, we integrate genetic, biological, developmental, psychosocial, societal, cultural, and intervention-based perspectives. Our review reveals substantial genetic overlap and some similar biological underpinnings for illbeing and wellbeing. In contrast, environmental factors and societal changes often have divergent impacts. We propose that future research should systematically assess both positive and negative aspects of mental health to discern their shared and unique determinants, predictors, mechanisms, and consequences.

• Borgen, Nicolai Topstad; Zachrisson, Henrik Daae; Lyngstad, Torkild Hovde; Cheesman, Rosa Catherine Gillespie & Ystrøm, Eivind (2024). For whom neighborhoods matter: Heterogeneous effects of socioeconomic neighborhood composition on child achievement. SocArXiv. doi: 10.31235/osf.io/fst58. Full text in Research Archive
• Mayerhofer, Lilian Juliane Kozlowski; Nes, Ragnhild Bang; Lan, Xiaoyu; Czajkowski, Nikolai Olavi; Ystrøm, Eivind & Røysamb, Espen (2024). Wellbeing and illbeing in women exposed to physical and sexual violence during peripregnancy: a population-based longitudinal study. European Journal of Psychotraumatology. 15(1). doi: 10.1080/20008066.2024.2398961. Full text in Research Archive Show summary

  Background: Physical and sexual violence against pregnant women have been associated with detrimental mental health outcomes for victims. Few studies have examined both positive (wellbeing) and negative (illbeing) mental health indicators in the same sample. Additionally, the literature assessing mental health based on different forms of violence is limited. Objective: To compare both wellbeing (life satisfaction) and illbeing (anxiety and depression) trajectories between non-victimized and victims of physical, sexual and both forms of violence that occurred during or shortly before pregnancy. Further, we analyse whether social support moderates these trajectories. Method: This longitudinal study is based on the Norwegian Mother, Father and Child Cohort, including the period from early pregnancy to toddlerhood (3 years). We compared wellbeing and illbeing trajectories of non-victims (n = 73,081), victims of physical abuse (n = 1076), sexual abuse (n = 683), and both forms of abuse (n = 107) using Growth Curve Modelling. Finally, social support was included as a moderator of wellbeing and illbeing trajectories. Results: Results indicated that victims scored systematically lower in wellbeing and higher in illbeing. Exposure to violence did not significantly change the wellbeing trajectory, pointing to similar developments in wellbeing among victims and non-victims for the considered period. On the other hand, different trajectories in illbeing occurred between victims and non-victims, as well as between victimized groups. Victims experienced greater change in illbeing scores, with a steeper decrease in illbeing compared to non-victims. Both victims and non-victims returned to respective baseline scores 3 years after birth. All women benefited from social support, but victims of physical abuse were particularly protected by social support. Conclusions: There is an alarming persistence of mental health problems in women exposed to violence during peripregnancy. Different forms of violence differentially impact women’s mental health. Social support is beneficial among all pregnant women.

• Kleppestø, Thomas Haarklau; Czajkowski, Nikolai Olavi; Sheehy-Skeffington, Jennifer; Vassend, Olav; Røysamb, Espen & Eftedal, Nikolai Haahjem [Show all 9 contributors for this article] (2024). The genetic underpinnings of right-wing authoritarianism and social dominance orientation explain political attitudes beyond Big Five personality. Journal of Personality. ISSN 0022-3506. 92(6), p. 1744–1758. doi: 10.1111/jopy.12921. Full text in Research Archive Show summary

  Objective: Political attitudes are predicted by the key ideological variables of right-wing authoritarianism (RWA) and social dominance orientation (SDO), as well as some of the Big Five personality traits. Past research indicates that personality and ideological traits are correlated for genetic reasons. A question that has yet to be tested concerns whether the genetic variation underlying the ideological traits of RWA and SDO has distinct contributions to political attitudes, or if genetic variation in political attitudes is subsumed under the genetic variation underlying standard Big Five personality traits. Method: We use data from a sample of 1987 Norwegian twins to assess the genetic and environmental relationships between the Big Five personality traits, RWA, SDO, and their separate contributions to political policy attitudes. Results: RWA and SDO exhibit very high genetic correlation (r = 0.78) with each other and some genetic overlap with the personality traits of openness and agreeableness. Importantly, they share a larger genetic substrate with political attitudes (e.g., deporting an ethnic minority) than do Big Five personality traits, a relationship that persists even when controlling for the genetic foundations underlying personality traits. Conclusion: Our results suggest that the genetic foundations of ideological traits and political attitudes are largely non-overlapping with the genetic foundations of Big Five personality traits.

• Verhoef, Ellen; Allegrini, Andrea G.; Jansen, Philip R.; Lange, Katherine; Wang, Carol A. & Morgan, Angela T. [Show all 64 contributors for this article] (2024). Genome-Wide Analyses of Vocabulary Size in Infancy and Toddlerhood: Associations With Attention-Deficit/Hyperactivity Disorder, Literacy, and Cognition-Related Traits. Biological Psychiatry. ISSN 0006-3223. 95(9), p. 859–869. doi: 10.1016/j.biopsych.2023.11.025. Full text in Research Archive
• Torvik, Fartein Ask; Sunde, Hans Fredrik; Cheesman, Rosa Catherine Gillespie; Eftedal, Nikolai Haahjem; Keller, Matthew C. & Ystrøm, Eivind [Show all 7 contributors for this article] (2024). Non-random mating patterns within and across education and mental and somatic health. Nature Communications. 15(1). doi: 10.1038/s41467-024-54966-9. Full text in Research Archive Show summary

  Partners resemble each other in health and education, but studies usually examine one trait at a time in established couples. Using data from all Norwegian first-time parents (N = 187,926) between 2016–2020, we analyse grade point average at age 16, educational attainment, and medical records of 10 mental and 10 somatic health conditions measured 10 to 5 years before childbirth. We find stronger partner similarity in mental (median r = 0.14) than in somatic health conditions (median r = 0.04), with ubiquitous cross-trait correlations in mental health (median r = 0.13). High grade point average or education is associated with better partner mental (median r = −0.16) and somatic (median r = −0.08) health. Elevated mental health correlations (median r = 0.25) in established couples indicate convergence. Analyses of siblings and in-laws suggest that health similarity is influenced by indirect assortment based on related traits. Adjusting for grade point average or education reduces partner health correlations by 30–40%. These findings have implications for the distribution of risk factors among children, genetic studies, and intergenerational transmission.

• Vollrath, Margarete E.; Eilertsen, Espen Moen; Torgersen, Svenn Omar; Gjerde, Line Cecilie & Ystrøm, Eivind (2024). Bridging Temperament and the Big Five in Children: A Genetically Informative Study. Journal of Personality and Social Psychology. ISSN 0022-3514. 126(4), p. 660–675. doi: 10.1037/pspp0000500. Full text in Research Archive Show summary

  Early temperament precedes children’s emerging Big Five personality, but shared models of temperament and personality are scarce. We wanted to estimate the genetic factor structure underlying both temperament and the Big Five in children, employing a genetically informed study. Within the Norwegian Mother and Child Cohort Study, we selected 26,354 twins, siblings, and cousins. Mothers rated their children’s temperament three times between the ages of 1.5 and 5 years, and the children’s Big Five personality at the age of 8. We analyzed the data using biometric modeling. The mean heritability of single-time temperamental traits and Big Five personality traits was .48 and .45, respectively. The mean genetic correlations of temperament across time were .80. The genetic correlations of temperament at 5 years and the Big Five at 8 years revealed two factors, the first comprising reversed Big Five Neuroticism, Agreeableness, Conscientiousness, and reversed EAS Emotionality, the second comprising Big Five Extraversion, Openness to Experience, EAS Activity, Sociability, and reversed Shyness. A confirmatory factor analysis estimated the two factors showing heritabilities of .96 and .72, respectively. The two factors mirrored the metatraits Stability and Plasticity by John M. Digman. Temperament and personality in childhood can be meaningfully bridged using just two metafactors.

• Bjørndal, Ludvig Daae; Eilertsen, Espen Moen; Ayorech, Ziada; Cheesman, Rosa; Ahmadzadeh, Yasmin I. & Baldwin, Jessie R. [Show all 13 contributors for this article] (2024). Disentangling direct and indirect genetic effects from partners and offspring on maternal depression using trio-GCTA. Nature Mental Health. 2(4), p. 417–425. doi: 10.1038/s44220-024-00207-3. Full text in Research Archive Show summary

  Maternal depressive symptoms are highly prevalent and can negatively impact affected individuals and family members. Understanding etiological influences on maternal depression, such as genetic liability, is key to inform treatment and prevention efforts. Here we quantified direct and indirect genetic effects (that is, when genetic variants in other individuals influence risk of maternal depression through the environment) from partners and offspring on maternal depressive symptoms at multiple time points using genome-wide complex trait analysis with parent–offspring trios. We used data from the Norwegian Mother, Father and Child cohort study, including up to 21,000 genotyped parent–offspring trios. Models with indirect genetic effects had best fit at three out of five time points (3, 5 and 8 years after birth). The variance in maternal depressive symptoms explained by direct genetic effects ranged from 5% to 14%, whereas indirect genetic effects explained 0–14% of variance across time points. Heritable traits in family members contribute to maternal depressive symptoms through the environment at several time points after birth.

• Dahl, Andreas; Eilertsen, Espen Moen; Cabello, Sara Fernandez Rodriguez; Norbom, Linn B.; Tandberg, Anneli Desire & Leonardsen, Esten [Show all 11 contributors for this article] (2024). Genetic and brain similarity independently predict childhood anthropometrics and neighborhood socioeconomic conditions. Developmental Cognitive Neuroscience. ISSN 1878-9293. 65. doi: 10.1016/j.dcn.2023.101339. Full text in Research Archive Show summary

  Linking the developing brain with individual differences in clinical and demographic traits is challenging due to the substantial interindividual heterogeneity of brain anatomy and organization. Here we employ an integrative approach that parses individual differences in both cortical thickness and common genetic variants, and assess their effects on a wide set of childhood traits. The approach uses a linear mixed model framework to obtain the unique effects of each type of similarity, as well as their covariance. We employ this approach in a sample of 7760 unrelated children in the ABCD cohort baseline sample (mean age 9.9, 46.8% female). In general, associations between cortical thickness similarity and traits were limited to anthropometrics such as height, weight, and birth weight, as well as a marker of neighborhood socioeconomic conditions. Common genetic variants explained significant proportions of variance across nearly all included outcomes, although estimates were somewhat lower than previous reports. No significant covariance of the effects of genetic and cortical thickness similarity was found. The present findings highlight the connection between anthropometrics as well as neighborhood socioeconomic conditions and the developing brain, which appear to be independent from individual differences in common genetic variants in this population-based sample.

• Kleppestø, Thomas Haarklau; Czajkowski, Nikolai Olavi; Vassend, Olav Mandt; Røysamb, Espen; Eftedal, Nikolai Haahjem & Sheehy-Skeffington, Jennifer [Show all 10 contributors for this article] (2024). Attachment and Political Personality are Heritable and Distinct Systems, and Both Share Genetics with Interpersonal Trust and Altruism. Behavior Genetics. ISSN 0001-8244. 54, p. 321–332. doi: 10.1007/s10519-024-10185-y. Full text in Research Archive Show summary

  The attachment and caregiving domains maintain proximity and care-giving behavior between parents and offspring, in a way that has been argued to shape people’s mental models of how relationships work, resulting in secure, anxious or avoidant interpersonal styles in adulthood. Several theorists have suggested that the attachment system is closely connected to orientations and behaviors in social and political domains, which should be grounded in the same set of familial experiences as are the different attachment styles. We use a sample of Norwegian twins (N = 1987) to assess the genetic and environmental relationship between attachment, trust, altruism, right-wing authoritarianism (RWA), and social dominance orientation (SDO). Results indicate no shared environmental overlap between attachment and ideology, nor even between the attachment styles or between the ideological traits, challenging conventional wisdom in developmental, social, and political psychology. Rather, evidence supports two functionally distinct systems, one for navigating intimate relationships (attachment) and one for navigating social hierarchies (RWA/SDO), with genetic overlap between traits within each system, and two distinct genetic linkages to trust and altruism. This is counter-posed to theoretical perspectives that link attachment, ideology, and interpersonal orientations through early relational experiences.

• Nivard, Michel G.; Belsky, Daniel W.; Harden, K. Paige; Baier, Tina; Andreassen, Ole A. & Ystrøm, Eivind [Show all 8 contributors for this article] (2024). More than nature and nurture, indirect genetic effects on children’s academic achievement are consequences of dynastic social processes. Nature Human Behaviour. 8, p. 771–778. doi: 10.1038/s41562-023-01796-2. Full text in Research Archive Show summary

  Families transmit genes and environments across generations. When parents’ genetics affect their children’s environments, these two modes of inheritance can produce an ‘indirect genetic effect’. Such indirect genetic effects may account for up to half of the estimated genetic variance in educational attainment. Here we tested if indirect genetic effects reflect within-nuclear-family transmission (‘genetic nurture’) or instead a multi-generational process of social stratification (‘dynastic effects’). We analysed indirect genetic effects on children’s academic achievement in their fifth to ninth years of schooling in N = 37,117 parent–offspring trios in the Norwegian Mother, Father, and Child Cohort Study (MoBa). We used pairs of genetically related families (parents were siblings, children were cousins; N = 10,913) to distinguish within-nuclear-family genetic-nurture effects from dynastic effects shared by cousins in different nuclear families. We found that indirect genetic effects on children’s academic achievement cannot be explained by processes that operate exclusively within the nuclear family.

• Tandberg, Anneli Desire; Dahl, Andreas; Norbom, Linn Bonaventure; Westlye, Lars Tjelta; Ystrøm, Eivind & Tamnes, Christian Krog [Show all 7 contributors for this article] (2024). Individual differences in internalizing symptoms in late childhood: A variance decomposition into cortical thickness, genetic and environmental differences. Developmental Science. ISSN 1363-755X. 27. doi: 10.1111/desc.13537. Full text in Research Archive Show summary

  The brain undergoes extensive development during late childhood and early adolescence. Cortical thinning is a prominent feature of this development, and some researchers have suggested that differences in cortical thickness may be related to internalizing symptoms, which typically increase during the same period. However, research has yielded inconclusive results. We utilized a new method that estimates the combined effect of individual differences in vertex-wise cortical thickness on internalizing symptoms. This approach allows for many small effects to be distributed across the cortex and avoids the necessity of correcting for multiple tests. Using a sample of 8763 children aged 8.9 to 11.1 from the ABCD study, we decomposed the total variation in caregiver-reported internalizing symptoms into differences in cortical thickness, additive genetics, and shared family environmental factors and unique environmental factors. Our results indicated that individual differences in cortical thickness accounted for less than 0.5% of the variation in internalizing symptoms. In contrast, the analysis revealed a substantial effect of additive genetics and family environmental factors on the different components of internalizing symptoms, ranging from 06% to 48% and from 0% to 34%, respectively. Overall, while this study found a minimal association between cortical thickness and internalizing symptoms, additive genetics, and familial environmental factors appear to be of importance for describing differences in internalizing symptoms in late childhood.

• Frach, Leonard; Barkhuizen, Wikus; Allegrini, Andrea G.; Ask, Helga; Hannigan, Laurie J. & Corfield, Elizabeth Claire [Show all 11 contributors for this article] (2024). Examining intergenerational risk factors for conduct problems using polygenic scores in the Norwegian Mother, Father and Child Cohort Study. Molecular Psychiatry. ISSN 1359-4184. 29, p. 951–961. doi: 10.1038/s41380-023-02383-7. Full text in Research Archive Show summary

  The aetiology of conduct problems involves a combination of genetic and environmental factors, many of which are inherently linked to parental characteristics given parents’ central role in children’s lives across development. It is important to disentangle to what extent links between parental heritable characteristics and children’s behaviour are due to transmission of genetic risk or due to parental indirect genetic influences via the environment (i.e., genetic nurture). We used 31,290 genotyped mother-father-child trios from the Norwegian Mother, Father and Child Cohort Study (MoBa), testing genetic transmission and genetic nurture effects on conduct problems using 13 polygenic scores (PGS) spanning psychiatric conditions, substance use, education-related factors, and other risk factors. Maternal or self-reports of conduct problems at ages 8 and 14 years were available for up to 15,477 children. We found significant genetic transmission effects on conduct problems for 12 out of 13 PGS at age 8 years (strongest association: PGS for smoking, β = 0.07, 95% confidence interval = [0.05, 0.08]) and for 4 out of 13 PGS at age 14 years (strongest association: PGS for externalising problems, β = 0.08, 95% confidence interval = [0.05, 0.11]). Conversely, we did not find genetic nurture effects for conduct problems using our selection of PGS. Our findings provide evidence for genetic transmission in the association between parental characteristics and child conduct problems. Our results may also indicate that genetic nurture via traits indexed by our polygenic scores is of limited aetiological importance for conduct problems—though effects of small magnitude or effects via parental traits not captured by the included PGS remain a possibility.

• Mayerhofer, Lilian Juliane Kozlowski; Nes, Ragnhild Bang; Yu, Baeksan; Ayorech, Ziada; Lan, Xiaoyu & Ystrøm, Eivind [Show all 7 contributors for this article] (2024). Stability and change in maternal wellbeing and illbeing from pregnancy to three years postpartum. Quality of Life Research. ISSN 0962-9343. 33, p. 2797–2808. doi: 10.1007/s11136-024-03730-z. Full text in Research Archive Show summary

  Purpose Motherhood affects women’s mental health, encompassing aspects of both wellbeing and illbeing. This study investigated stability and change in wellbeing (i.e., relationship satisfaction and positive affect) and illbeing (i.e., depressive and anxiety symptoms) from pregnancy to three years postpartum. We further investigated the mutual and dynamic relations between these constructs over time and the role of genetic propensities in their time-invariant stability. Data and methods This four-wave longitudinal study included 83,124 women from the Norwegian Mother, Father, and Child Cohort Study (MoBa) linked to the Medical Birth Registry of Norway. Data were collected during pregnancy (30 weeks) and at 6, 18 and 36 months postpartum. Wellbeing and illbeing were based on the Relationship Satisfaction Scale, the Differential Emotions Scale and Hopkins Symptoms Checklist-8. Genetics were measured by the wellbeing spectrum polygenic index. Analyses were based on random intercept cross-lagged panel models using R. Results All four outcomes showed high stability and were mutually interconnected over time, with abundant cross-lagged predictions. The period of greatest instability was from pregnancy to 6 months postpartum, followed by increasing stability. Prenatal relationship satisfaction played a crucial role in maternal mental health postpartum. Women’s genetic propensity to wellbeing contributed to time-invariant stability of all four constructs. Conclusion Understanding the mutual relationship between different aspects of wellbeing and illbeing allows for identifying potential targets for health promotion interventions. Time-invariant stability was partially explained by genetics. Maternal wellbeing and illbeing develop in an interdependent way from pregnancy to 36 months postpartum.

• Sunde, Hans Fredrik; Eftedal, Nikolai Haahjem; Cheesman, Rosa; Corfield, Elizabeth C.; Kleppestø, Thomas H. & Seierstad, Anne Caroline [Show all 9 contributors for this article] (2024). Genetic similarity between relatives provides evidence on the presence and history of assortative mating. Nature Communications. 15(1). doi: 10.1038/s41467-024-46939-9. Full text in Research Archive Show summary

  Assortative mating – the non-random mating of individuals with similar traits – is known to increase trait-specific genetic variance and genetic similarity between relatives. However, empirical evidence is limited for many traits, and the implications hinge on whether assortative mating has started recently or many generations ago. Here we show theoretically and empirically that genetic similarity between relatives can provide evidence on the presence and history of assortative mating. First, we employed path analysis to understand how assortative mating affects genetic similarity between family members across generations, finding that similarity between distant relatives is more affected than close relatives. Next, we correlated polygenic indices of 47,135 co-parents from the Norwegian Mother, Father, and Child Cohort Study (MoBa) and found genetic evidence of assortative mating in nine out of sixteen examined traits. The same traits showed elevated similarity between relatives, especially distant relatives. Six of the nine traits, including educational attainment, showed greater genetic variance among offspring, which is inconsistent with stable assortative mating over many generations. These results suggest an ongoing increase in familial similarity for these traits. The implications of this research extend to genetic methodology and the understanding of social and economic disparities.

• Ayorech, Ziada; Torvik, Fartein Ask; Cheesman, Rosa; Eilertsen, Espen M.; Valstad, Mathias & Bjørndal, Ludvig Daae [Show all 9 contributors for this article] (2024). The structure of psychiatric comorbidity without selection and assortative mating. Translational Psychiatry. 14(1), p. 1–9. doi: 10.1038/s41398-024-02768-4. Full text in Research Archive
• Arneberg, Vilde Sofie; Sundsvold, Vilde; Bjørndal, Ludvig Daae & Ystrøm, Eivind (2024). Borderline Personality Disorder Symptoms and Stressful Life Events: An Evaluation of Gene-Environment Interplay. Biological Psychiatry: Global Open Science. 4(6). doi: 10.1016/j.bpsgos.2024.100390. Full text in Research Archive Show summary

  Background Borderline personality disorder (BPD) is associated with high rates of stressful life events (SLEs). It is unclear whether people who experience SLEs have more BPD symptoms after accounting for the effects of familial risk factors. Our aims in the current study were to 1) create a predictive model of BPD using stressors across age and contexts and 2) examine whether SLEs resulted in higher levels of BPD symptoms beyond the effects of genetic and environmental risk factors. Methods The sample comprised 2801 twins from the Norwegian Institute of Public Health Twin Panel. Poisson regression was used to explore which SLEs predicted BPD symptoms. Elastic net penalized regression was conducted to develop a predictive model for SLEs and BPD symptoms. Co-twin control analyses were performed to differentiate between environmental and genetic factors. Results SLEs experienced during childhood and adulthood were associated with BPD symptoms. A weighted polyevent risk score explained 22% of the total variation in symptoms. Shared environmental and heritable factors explained 31% and 47% of individual differences in BPD symptomatology, respectively. Measured SLEs explained 42% of the shared environmental risk for BPD. The predictive risk of SLEs for BPD was reduced when shared environmental and genetic factors were accounted for. However, SLEs increased risk of BPD symptoms beyond the effects of shared genetic and environmental factors. Conclusions BPD symptomatology following SLEs cannot fully be explained by genetic and shared environmental factors. The SLE-BPD symptoms associations were primarily due to selection by family environments. It is important to identify familial factors that lead to both SLEs and BPD symptoms. SLEs remained associated with BPD symptoms beyond genetic and environmental confounding.

• Hughes, Amanda M.; Torvik, Fartein Ask; Bergen, Elsje van; Hannigan, Laurie John; Corfield, Elizabeth Claire & Andreassen, Ole A. [Show all 11 contributors for this article] (2024). Parental education and children’s depression, anxiety, and ADHD traits, a within-family study in MoBa. npj Science of learning. 9. doi: 10.1038/s41539-024-00260-8. Full text in Research Archive Show summary

  Children born to parents with fewer years of education are more likely to have depression, anxiety, and attention-deficit hyperactivity disorder (ADHD), but it is unclear to what extent these associations are causal. We estimated the effect of parents’ educational attainment on children’s depressive, anxiety, and ADHD traits at age 8 years, in a sample of 40,879 Norwegian children born in 1998–2009 and their parents. We used within-family Mendelian randomization, which employs genetic variants as instrumental variables, and controlled for direct genetic effects by adjusting for children’s polygenic indexes. We found little evidence that mothers’ or fathers’ educational attainment independently affected children’s depressive, anxiety, or ADHD traits. However, children’s own polygenic scores for educational attainment were independently and negatively associated with these traits. Results suggest that differences in these traits according to parents’ education may reflect direct genetic effects more than genetic nurture. Consequences of social disadvantage for children’s mental health may however be more visible in samples with more socioeconomic variation, or contexts with larger socioeconomic disparities than present-day Norway. Further research is required in populations with more educational and economic inequality and in other age groups.

• Ahmadzadeh, Y. I.; Eilertsen, E. M.; Cheesman, R.; Rayner, C.; Ystrom, E. & Hannigan, L. J. [Show all 7 contributors for this article] (2023). Mothers' symptoms of anxiety and depression and the development of child temperament: A genetically informative, longitudinal investigation. JCPP Advances. 3(4), p. 1–12. doi: 10.1002/jcv2.12171. Full text in Research Archive Show summary

  Background Child temperament traits and mothers' emotional symptoms relating to anxiety and depression may drive changes in one another, leading to their ‘co-development’ across time. Alternatively, links between mother and child traits may be attributable to shared genetic propensities. We explored longitudinal associations between mothers' emotional symptoms and child temperament traits and adjusted for genetic effects shared across generations. Methods This study is based on the Norwegian Mother, Father and Child Cohort Study (MoBa). Mothers (n = 34,060) reported on their symptoms of anxiety and depression, and temperament among offspring (n = 42,526), at child ages 1.5, 3 and 5 years. Structural equation models parameterised developmental change in traits, and an extended family design adjusted for genetic effects. Results We found individual differences in stable trait scores and rate of change for all study variables. Longitudinal stability in mothers' emotional symptoms was associated with longitudinal stability in offspring emotionality (r = 0.143), shyness (r = 0.031), and sociability (r = −0.015). Longitudinal change in mothers' symptoms showed very small or negligible correlations with longitudinal change in child temperament. Both genetic and environmental influences explained the stable longitudinal association between mothers' symptoms and child emotionality. Conclusions The studied associations between mother and child traits across time appeared to be due to stable, trait-like factors, involving genetic and environmental influence, rather than their co-development. Findings contribute knowledge on how emotional symptoms develop in families across time, and the methods with which we can explore such development.

• Hannigan, Laurie; Lund, Ingunn Olea; Askelund, Jo Adrian Dahl; Ystrøm, Eivind; Corfield, Elizabeth Claire & Ask, Helga [Show all 7 contributors for this article] (2023). Genotype-environment interplay in associations between maternal drinking and offspring emotional and behavioral problems. Psychological Medicine. ISSN 0033-2917. 54(1), p. 203–214. doi: 10.1017/S0033291723003057. Full text in Research Archive Show summary

  Background While maternal at-risk drinking is associated with children's emotional and behavioral problems, there is a paucity of research that properly accounts for genetic confounding and gene–environment interplay. Therefore, it remains uncertain what mechanisms underlie these associations. We assess the moderation of associations between maternal at-risk drinking and childhood emotional and behavioral problems by common genetic variants linked to environmental sensitivity (genotype–environment [G × E] interaction) while accounting for shared genetic risk between mothers and offspring (G × E correlation). Methods We use data from 109 727 children born to 90 873 mothers enrolled in the Norwegian Mother, Father, and Child Cohort Study. Women self-reported alcohol consumption and reported emotional and behavioral problems when children were 1.5/3/5 years old. We included child polygenic scores (PGSs) for traits linked to environmental sensitivity as moderators. Results Associations between maternal drinking and child emotional (β1 = 0.04 [95% confidence interval (CI) 0.03–0.05]) and behavioral (β1 = 0.07 [0.06–0.08]) outcomes attenuated after controlling for measured confounders and were almost zero when we accounted for unmeasured confounding (emotional: β1 = 0.01 [0.00–0.02]; behavioral: β1 = 0.01 [0.00–0.02]). We observed no moderation of these adjusted exposure effects by any of the PGS. Conclusions The lack of strong evidence for G × E interaction may indicate that the mechanism is not implicated in this kind of intergenerational association. It may also reflect insufficient power or the relatively benign nature of the exposure in this sample.

• Cheesman, Rosa Catherine Gillespie; Ayorech, Ziada; Eilertsen, Espen Moen & Ystrøm, Eivind (2023). Why we need families in genomic research on developmental psychopathology. JCPP Advances. 3(1). doi: 10.1002/jcv2.12138. Full text in Research Archive Show summary

  Background Fundamental questions about the roles of genes, environments, and their interplay in developmental psychopathology have traditionally been the domain of twin and family studies. More recently, the rapidly growing availability of large genomic datasets, composed of unrelated individuals, has generated novel insights. However, there are major stumbling blocks. Only a small fraction of the total genetic influence on childhood psychopathology estimated from family data is captured with measured DNA. Moreover, genetic influence identified using DNA is often confounded with indirect genetic effects of relatives, population stratification and assortative mating. Methods The goal of this paper is to review how combining DNA-based genomic research with family-based quantitative genetics helps to address key issues in genomics and push knowledge further. Results We focus on three approaches to obtaining more accurate and novel genomic findings on the developmental aetiology of psychopathology: (a) using knowledge from twin and family studies, (b) triangulating with twin and family studies, and (c) integrating data and methods with twin and family studies. Conclusion We support the movement towards family-based genomic research, and show that developmental psychologists are particularly well-placed to contribute hypotheses, analysis tools, and data.

• Yu, Baeksan; Zachrisson, Henrik Daae; Cheesman, Rosa Catherine Gillespie; Ystrøm, Eivind & Nes, Ragnhild Bang (2023). Boys with overweight status lagged behind girls with overweight status in reading: evidence from mendelian randomization. Journal of Clinical Epidemiology. ISSN 0895-4356. 159, p. 199–205. doi: 10.1016/j.jclinepi.2023.05.001. Full text in Research Archive Show summary

  Objectives We investigated the relationship between childhood weight status and academic achievement across sexes and different school subjects in Norway. Study Design and Setting We used data from the Norwegian Mother, Father and Child Cohort Study (MoBa), which includes genetic data (N = 13,648, 8-year-old children). We employed within-family mendelian randomization, using a body mass index (BMI) polygenic risk score as an instrument to address unobserved heterogeneity. Results Contrary to most previous findings, we observed that overweight status (including obesity) has more detrimental effects on reading achievement in boys than in girls; the test scores of boys with overweight were about a standard deviation lower than those of normal weight boys, and the negative effects on reading achievement became stronger in the later grade. Conclusion Previous obesity prevention studies have mainly targeted girls, based on the assumption that the obesity penalty is greater for girls. Our findings highlight that particular attention to boys with overweight may help reduce the existing gender gap in academic achievement.

• Mayerhofer, Lilian Juliane Kozlowski; Nes, Ragnhild Bang; Lan, Xiaoyu; Czajkowski, Nikolai Olavi; Ystrøm, Eivind & Røysamb, Espen (2023). Wellbeing and illbeing in women exposed to physical and sexual violence: A population based longitudinal study. OSF Preprints. Full text in Research Archive
• Wiker, Thea; Norbom, Linn B.; Beck, Dani; Agartz, Ingrid; Andreassen, Ole A. & Alnæs, Dag [Show all 14 contributors for this article] (2023). Reaction Time Variability in Children Is Specifically Associated With Attention Problems and Regional White Matter Microstructure. Biological Psychiatry: Cognitive Neuroscience and Neuroimaging. ISSN 2451-9022. 8(8), p. 832–840. doi: 10.1016/j.bpsc.2023.03.010. Full text in Research Archive Show summary

  Background Increased intraindividual variability (IIV) in reaction times (RTs) has been suggested as a key cognitive and behavioral marker of attention problems, but findings for other dimensions of psychopathology are less consistent. Moreover, while studies have linked IIV to brain white matter microstructure, large studies testing the robustness of these associations are needed. Methods We used data from the Adolescent Brain Cognitive Development (ABCD) Study baseline assessment to test the associations between IIV and psychopathology (n = 8622, age = 8.9–11.1 years) and IIV and white matter microstructure (n = 7958, age = 8.9–11.1 years). IIV was investigated using an ex-Gaussian distribution analysis of RTs in correct response go trials in the stop signal task. Psychopathology was measured by the Child Behavior Checklist and a bifactor structural equation model was performed to extract a general p factor and specific factors reflecting internalizing, externalizing, and attention problems. To investigate white matter microstructure, fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity were examined in 23 atlas-based tracts. Results Increased IIV in both short and long RTs was positively associated with the specific attention problems factor (Cohen’s d = 0.13 and d = 0.15, respectively). Increased IIV in long RTs was also positively associated with radial diffusivity in the left and right corticospinal tract (both tracts, d = 0.12). Conclusions Using a large sample and a data-driven dimensional approach to psychopathology, the results provide novel evidence for a small but specific association between IIV and attention problems in children and support previous findings on the relevance of white matter microstructure for IIV.

• Bromley, Rebecca; Graz, Myriam Bickle; Bluett-Duncan, Matthew; Chambers, C.; Damkier, P. & Dietrich, K. [Show all 26 contributors for this article] (2023). Expert consensus on neurodevelopmental outcomes in pregnancy pharmacovigilance studies. Frontiers in Pharmacology. 14. doi: 10.3389/fphar.2023.1094698. Full text in Research Archive Show summary

  Background: Exposure in utero to certain medications can disrupt processes of fetal development, including brain development, leading to a continuum of neurodevelopmental difficulties. Recognizing the deficiency of neurodevelopmental investigations within pregnancy pharmacovigilance, an international Neurodevelopmental Expert Working Group was convened to achieve consensus regarding the core neurodevelopmental outcomes, optimization of methodological approaches and barriers to conducting pregnancy pharmacovigilance studies with neurodevelopmental outcomes. Methods: A modified Delphi study was undertaken based on stakeholder and expert input. Stakeholders (patient, pharmaceutical, academic and regulatory) were invited to define topics, pertaining to neurodevelopmental investigations in medication-exposed pregnancies. Experts were identified for their experience regarding neurodevelopmental outcomes following medicinal, substances of misuse or environmental exposures in utero . Two questionnaire rounds and a virtual discussion meeting were used to explore expert opinion on the topics identified by the stakeholders. Results: Twenty-five experts, from 13 countries and professionally diverse backgrounds took part in the development of 11 recommendations. The recommendations focus on the importance of neurodevelopment as a core feature of pregnancy pharmacovigilance, the timing of study initiation and a core set of distinct but interrelated neurodevelopmental skills or diagnoses which require investigation. Studies should start in infancy with an extended period of investigation into adolescence, with more frequent sampling during rapid periods of development. Additionally, recommendations are made regarding optimal approach to neurodevelopmental outcome measurement, comparator groups, exposure factors, a core set of confounding and mediating variables, attrition, reporting of results and the required improvements in funding for potential later emerging effects. Different study designs will be required depending on the specific neurodevelopmental outcome type under investigation and whether the medicine in question is newly approved or already in widespread use. Conclusion: An improved focus on neurodevelopmental outcomes is required within pregnancy pharmacovigilance. These expert recommendations should be met across a complementary set of studies which converge to form a comprehensive set of evidence regarding neurodevelopmental outcomes in pregnancy pharmacovigilance.

• Wechsler, Daniel L.; Rijsdijk, Fruhling V.; Adamo, Nicoletta; Eilertsen, Espen Moen; Ahmadzadeh, Yasmin I. & Badini, Isabella [Show all 9 contributors for this article] (2023). Assessing aetiological overlap between child and adult attention-deficit hyperactivity disorder symptoms in an extended family design. BJPsych Open. 9(5), p. 1–7. doi: 10.1192/bjo.2023.554. Full text in Research Archive Show summary

  Background Several longitudinal studies have cast doubt on the aetiological overlap between child and adult attention-deficit hyperactivity disorder (ADHD). However, a lack of genetically sensitive data following children across adulthood precludes direct evaluation of aetiological overlap between child and adult ADHD. Aims We circumvent the existing gap in longitudinal data by exploring genetic overlap between maternal (adult) and offspring (child) ADHD and comorbid symptoms in an extended family cohort. Method Data were drawn from the Norwegian Mother, Father and Child Cohort Study, a Norwegian birth registry cohort of 114 500 children and their parents. Medical Birth Registry of Norway data were used to link extended families. Mothers self-reported their own ADHD symptoms when children were aged 3 years; reported children's ADHD symptoms at age 5 years; and children's ADHD, oppositional defiant disorder (ODD), conduct disorder, anxiety and depression symptoms at age 8 years. Genetic correlations were derived from Multiple-Children-of-Twins-and-Siblings and extended bivariate twin models. Results Phenotypic correlations between adult ADHD symptoms and child ADHD, ODD, conduct disorder, anxiety and depression symptoms at age 8 years were underpinned by medium-to-large genetic correlations (child ADHD: rG = 0.55, 95% CI 0.43−0.93; ODD: rG = 0.80, 95% CI 0.46−1; conduct disorder: rG = 0.44, 95% CI 0.28−1; anxiety: rG = 0.72, 95% CI 0.48−1; depression: rG = 1, 95% CI 0.66−1). These cross-generational adult–child genetic correlations were of a comparable magnitude to equivalent child–child genetic correlations with ADHD symptoms at age 5 years. Conclusions Our findings provide genetically sensitive evidence that ADHD symptoms in adulthood share a common genetic architecture with symptoms of ADHD and four comorbid disorders at age 8 years. These findings suggest that in the majority of cases, ADHD symptoms in adulthood are not aetiologically distinct from in childhood.

• Gjerde, Line Cecilie; Eilertsen, Espen Moen; McAdams, Tom A.; Cheesman, Rosa Catherine Gillespie; Moffitt, Terrie & Caspi, Avshalom [Show all 10 contributors for this article] (2023). The p factor of psychopathology and personality in middle childhood: genetic and gestational risk factors. Psychological Medicine. ISSN 0033-2917. 53(9), p. 4275–4285. doi: 10.1017/S0033291723000077. Full text in Research Archive Show summary

  Background A joint, hierarchical structure of psychopathology and personality has been reported in adults but should also be investigated at earlier ages, as psychopathology often develops before adulthood. Here, we investigate the joint factor structure of psychopathology and personality in eight-year-old children, estimate factor heritability and explore external validity through associations with established developmental risk factors. Methods Phenotypic and biometric exploratory factor analyses with bifactor rotation on genetically informative data from the Norwegian Mother, Father, and Child Cohort (MoBa) study. The analytic sub-sample comprised 10 739 children (49% girls). Mothers reported their children's symptoms of depression (Short Moods and Feelings Questionnaire), anxiety (Screen for Anxiety Related Disorders), attention-deficit/hyperactivity disorder inattention and hyperactivity, oppositional-defiant disorder, conduct disorder (Parent/Teacher Rating Scale for Disruptive Behavior Disorders), and Big Five personality (short Hierarchical Personality Inventory for Children). Developmental risk factors (early gestational age and being small for gestational age) were collected from the Medical Birth Registry. Results Goodness-of-fit indices favored a p factor model with three residual latent factors interpreted as negative affectivity, positive affectivity, and antagonism, whereas psychometric indices favored a one-factor model. ADE solutions fitted best, and regression analyses indicated a negative association between gestational age and the p factor, for both the one- and four-factor solutions. Conclusion Correlations between normative and pathological traits in middle childhood mostly reflect one heritable and psychometrically interpretable p factor, although optimal fit to data required less interpretable residual latent factors. The association between the p factor and low gestational age warrants further study of early developmental mechanisms.

• Liu, Chaoyu; Ystrøm, Eivind & McAdams, Thomas Andrew (2023). Long-Term Maternal and Child Outcomes Following Postnatal SSRI Treatment. JAMA Network Open. 6(8), p. 1–14. doi: 10.1001/jamanetworkopen.2023.31270. Full text in Research Archive Show summary

  Importance Although selective serotonin reuptake inhibitors (SSRIs) are recommended for postnatal depression treatment, there is a lack of evidence regarding long-term maternal and child outcomes following postnatal SSRI treatment. Objective To examine whether postnatal SSRI treatment moderated postnatal depression–associated maternal and child outcomes across early childhood years. Design, Setting, and Participants This cohort study used longitudinal data from the Norwegian Mother, Father and Child Cohort Study. Participating women were recruited in weeks 17 to 18 of pregnancy from 1999 to 2008 and were prospectively followed up after childbirth. Data analysis was performed between December 2021 to October 2022. Exposure Postnatal depression diagnosis (a binary indicator of eligibility for treatment) was defined as a score of 7 or greater on the 6-item version of the Edinburgh Postnatal Depression Scale. The Hopkins Symptom Checklist was used as a continuous indicator of and postnatal depressive symptomology at postpartum month 6. Postnatal SSRI treatment was identified using self-reported data at postpartum month 6. Main Outcomes and Measures Maternal outcomes included self-reported depression symptomology and relationship satisfaction from childbirth to postpartum year 5. Child outcomes included maternal-report internalizing and externalizing problems, attention-deficit/hyperactivity disorder symptoms, and motor and language development at ages 1.5, 3, and 5 years. A propensity score adjustment method was used to control for prenatal factors associated with postnatal SSRI exposure probability. Results Among a total of 61 081 mother-child dyads, 8671 (14.2%) (mean [SD] age, 29.93 [4.76] years) met the criteria for postnatal depression diagnosis, 177 (2.0%) (mean [SD] age, 30.20 [5.01] years) of whom received postnatal SSRI treatment. More severe postnatal depression symptomology was associated with a range of adverse maternal and child outcomes. Focusing analyses only on the postnatal depression dyads indicated that postnatal SSRI treatment attenuated negative associations between postnatal depression and maternal relationship satisfaction at postpartum month 6 (moderation β, 0.13; 95% CI, 0.07-0.19), years 1.5 (moderation β, 0.11; 95% CI, 0.05-0.18) and 3 (moderation β, 0.12; 95% CI, 0.04-0.19), and for child ADHD at age 5 years (moderation β, −0.15; 95% CI, −0.24 to −0.05). Postnatal SSRI treatment mitigated the negative associations between postnatal depression and maternal depression, partner relationship satisfaction, child externalizing problems, and attention-deficit/hyperactivity disorder up to 5 years after childbirth. Conclusions and Relevance The results of this large prospective cohort study suggest that postnatal SSRI treatment was associated with a reduced risk of postnatal depression–associated maternal mental health problems and child externalizing behaviors across early childhood years. These findings suggest that postnatal SSRI treatment may bring benefits in the long term to women with postnatal depression and their offspring. This study potentially provides valuable information for clinicians and women with postnatal depression to make informed treatment decisions.

• Jami, Eshim S.; Hammerschlag, Anke R.; Sallis, Hannah M.; Qiao, Zhen; Andreassen, Ole & Magnus, Per Minor [Show all 14 contributors for this article] (2023). Do environmental effects indexed by parental genetic variation influence common psychiatric symptoms in childhood? Translational Psychiatry. 13. doi: 10.1038/s41398-023-02348-y. Full text in Research Archive Show summary

  Parental genes may indirectly influence offspring psychiatric outcomes through the environment that parents create for their children. These indirect genetic effects, also known as genetic nurture, could explain individual differences in common internalising and externalising psychiatric symptoms during childhood. Advanced statistical genetic methods leverage data from families to estimate the overall contribution of parental genetic nurture effects. This study included up to 10,499 children, 5990 mother–child pairs, and 6,222 father–child pairs from the Norwegian Mother Father and Child Study. Genome-based restricted maximum likelihood (GREML) models were applied using software packages GCTA and M-GCTA to estimate variance in maternally reported depressive, disruptive, and attention-deficit hyperactivity disorder (ADHD) symptoms in 8-year-olds that was explained by direct offspring genetic effects and maternal or paternal genetic nurture. There was no strong evidence of genetic nurture in this sample, although a suggestive paternal genetic nurture effect on offspring depressive symptoms (variance explained (V) = 0.098, standard error (SE) = 0.057) and a suggestive maternal genetic nurture effect on ADHD symptoms (V = 0.084, SE = 0.058) was observed. The results indicate that parental genetic nurture effects could be of some relevance in explaining individual differences in childhood psychiatric symptoms. However, robustly estimating their contribution is a challenge for researchers given the current paucity of large-scale samples of genotyped families with information on childhood psychiatric outcomes.

• Constantinou, Andrea; Soest, Tilmann Martin von; Zachrisson, Henrik Daae; Torvik, Fartein Ask; Cheesman, Rosa Catherine Gillespie & Ystrøm, Eivind (2023). Childhood personality and academic performance: A sibling fixed-effects study. Journal of Personality. ISSN 0022-3506. p. 1–13. doi: 10.1111/jopy.12900. Full text in Research Archive Show summary

  Objective: This study investigated the associations between personality traits at age 8 and academic performance between ages 10 and 14, controlling for family confounds. Background: Many studies have shown links between children’s personality traits and their school performance. However, we lack evidence on whether these associations remain after genetic and environmental confounders are accounted for. Method: Sibling data from the Norwegian Mother and Child Cohort Study (MoBa) were used (n = 9701). First, we estimated the overall associations be- tween Big Five personality traits and academic performance, including literacy, numeracy, and foreign language. Second, we added sibling fixed effects to remove unmeasured confounders shared by siblings as well as rating bias. Results: Openness to Experience (between-person β = 0.22 [95% CI: 0.21–0.24]) and Conscientiousness (between-person β = 0.18 [95% CI 0.16–0.20]) were most strongly related to educational performance. Agreeableness (between-per- son β = 0.06 [95% CI −0.08–0.04]) and Extraversion (between-person β = 0.02 [95% CI 0.00–0.04]) showed small associations with educational performance. Neuroticism had a moderate negative association (between-person β = −0.14 [95% CI −0.15–0.11]). All associations between personality and performance were ro- bust to confounding: the within-family estimates from sibling fixed-effects mod- els overlapped with the between-person effects. Finally, childhood personality was equally predictive of educational performance across ages and genders. Conclusions: Although family background is influential for academic achieve- ment, it does not confound associations with personality. Childhood personal- ity traits reflect unbiased and consistent individual differences in educational potential.

• Ayorech, Ziada; Cheesman, Rosa; Eilertsen, Espen M.; Bjørndal, Ludvig Daae; Røysamb, Espen & McAdams, Tom A. [Show all 8 contributors for this article] (2023). Maternal depression and the polygenic p factor: A family perspective on direct and indirect effects. Journal of Affective Disorders. ISSN 0165-0327. 332, p. 159–167. doi: 10.1016/j.jad.2023.03.043. Full text in Research Archive Show summary

  Within-family studies typically assess indirect genetic effects of parents on children, however social support theory points to a critical role of partners and children on women's depression. To address this research gap and account for the high heterogeneity of depression, we calculated a general psychiatric factor using eleven major psychiatric polygenic scores (polygenic p), in up to 25,000 parent-offspring trios from the Norwegian Mother, Father and Child Cohort Study (MoBa). Multilevel modeling of trio polygenic p was used to distinguish direct and indirect genetic effects on mothers depression during pregnancy (gestational age 17 and 30 weeks), infancy (6 months, 18 months) and early childhood (3 years, 5 years, and 8 years). We found mothers polygenic p predicts their depression symptoms (b = 0.092; 95 % CI [0.087,0.098]), outperforming prediction using a single major depressive disorder polygenic score (b = 0.070, 95 % CI [0.066,0.075]). Jointly modeling trio polygenic p revealed indirect genetic effects of fathers (b = 0.022, 95 % CI [0.014,0.030]) and children (b = 0.021, 95 % CI [0.010,0.037]) on mothers' depression. Our results support the generalizability of polygenic effects across mental health and highlight the role of close family members on women's depression.

• Askelund, Adrian Dahl; Ask, Helga; Ystrøm, Eivind; Havdahl, Alexandra & Hannigan, Laurie John (2023). Exploring the differentiation of behavioural and emotional problems across childhood: A prospective longitudinal cohort study. JCPP Advances. 3(4), p. 1–11. doi: 10.1002/jcv2.12176. Full text in Research Archive
• Samuelsen, Kristin; Ystrøm, Eivind; Gjerde, Line Cecilie & Eilertsen, Espen Moen (2023). Kind of blue – An evaluation of etiologies for prenatal versus postnatal depression symptoms. Journal of Affective Disorders. ISSN 0165-0327. 335, p. 305–312. doi: 10.1016/j.jad.2023.04.135. Full text in Research Archive Show summary

  Prenatal and postnatal depression potentially have severe consequences, but we do not know to what extent they have the same etiological factors. Genetically informative designs yield insight into common etiology between pre- and postnatal depression and inform on potential prevention and intervention efforts. This study evaluates the overlap in genetic and environmental factors in pre- and postnatal depression symptoms. Methods We conducted univariate and bivariate modeling, using a quantitative, extended twin study. The sample was a subsample of the MoBa prospective pregnancy cohort study in 6039 pairs of related women. Measurement was conducted at week 30 of pregnancy and 6 months following delivery, using a self-report scale. Results The heritability of depressive symptoms was 16.2 % (95 % CI = 10.7–22.1) prenatally and 25.7 % (95 % CI = 19.2–32.2) postnatally. The correlation between risk factors for prenatal and postnatal depressive symptoms was at unity ( r = 1.00) for genetic effects, and at disunity ( r = 0.36) for environmental effects. The genetic effects for postnatal depressive symptoms were 1.7 times larger compared to prenatal depressive symptoms. Limitations Although genes for depression become more influential postpartum, only future studies can inform on the mechanisms for such a socio-biological augmentation of effect. Conclusion Genetic risk factors for prenatal and postnatal depressive symptoms are indistinguishable in kind, with greater impact after birth, whereas environmental risk factors for depression symptoms are mostly non-overlapping before and after birth. These findings indicate that interventions could be of different kind before and after birth.

• Kleppestø, Thomas Haarklau; Eilertsen, Espen Moen; Bergen, Elsje van; Sunde, Hans Fredrik; Zietsch, Brendan & Nordmo, Magnus [Show all 10 contributors for this article] (2023). Intergenerational transmission of ADHD behaviors: Genetic and environmental pathways. Psychological Medicine. ISSN 0033-2917. 54, p. 1309–1317. doi: 10.1017/S003329172300315X. Full text in Research Archive
• Røysamb, Espen; Moffitt, Terrie; Caspi, Avshalom; Ystrøm, Eivind & Nes, Ragnhild Bang (2023). Worldwide Well-Being: Simulated Twins Reveal Genetic and (Hidden) Environmental Influences. Perspectives on Psychological Science. ISSN 1745-6916. 18(6), p. 1562–1574. doi: 10.1177/17456916231178716. Full text in Research Archive Show summary

  What are the major sources of worldwide variability in subjective well-being (SWB)? Twin and family studies of SWB have found substantial heritability and strong effects from unique environments but virtually no effects from shared environments. However, extant findings are not necessarily valid at the global level. Prior studies have examined within-countries variability but did not take into account mean differences across nations. In this article, we aim to estimate the effects of genetic factors, individual environmental exposures, and shared environments for the global population. We combine a set of knowns from national well-being studies (means and standard deviations) and behavioral-genetic studies (heritability) to model a scenario of twin studies across 157 countries. For each country, we simulate data for a set of twin pairs and pool the data into a global sample. We find a worldwide heritability of 31% to 32% for SWB. Individual environmental factors explain 46% to 52% of the variance (including measurement error), and shared environments account for 16% to 23% of the global variance in SWB. Worldwide, well-being is somewhat less heritable than within nations. In contrast to previous within-countries studies, we find a notable effect of shared environments. This effect is not limited to within families but operates at a national level.

• Tesli, Martin Steen; Nesvåg, Ragnar; Haukvik, Unn Kristin Hansen; Gustavson, Kristin; Tesli, Natalia & Friestad, Christine [Show all 12 contributors for this article] (2023). Common genetic and environmental risk for personality disorders and psychotic-like experiences in young adult twins. Acta Psychiatrica Scandinavica. ISSN 0001-690X. 148(6), p. 561–569. doi: 10.1111/acps.13596. Full text in Research Archive Show summary

  Abstract Introduction Psychotic‐like experiences (PLE) have been associated with the subsequent emergence of psychotic disorders as well as several other domains of psychopathology. In this twin study, we estimated the genetic and environmental correlations between PLE and 10 personality disorders (PD). Methods Diagnoses of 10 PDs according to the Diagnostic and Statistical Manual of Mental Disorders (DSM‐IV) and PLE from the Composite International Diagnostic Interview (CIDI) were retrieved for 2793 young adult twins from the Norwegian Twin Registry. Risk for having a PD and PLEs was modeled using item response theory. Biometric twin models were fitted to estimate the genetic and environmental correlations between PDs and PLEs. Co‐twin control analysis was performed to estimate additional within‐family risk for PLEs when having a PD. Results Phenotypic overlap between PDs and PLEs ranged from 14% to 44% in males and from 11% to 39% in females, with the highest overlap for borderline PD in both sexes. In general, we found higher genetic correlations ( r  = 0.14–0.72) than environmental correlations ( r  = 0.06–0.28) between PDs and PLEs. The highest genetic correlations between PLE and PDs were found for borderline ( r  = 0.72), paranoid ( r  = 0.56), schizotypal ( r  = 0.56) and antisocial PD (r = 0.49). Conclusion We found that the co‐occurrence between PDs and PLE is the best explained by shared genetic determinants, with minor contributions from environmental factors. Interestingly, borderline PD was highly genetically correlated with PLE, warranting molecular genetic studies of this association.

• Badini, Isabella; Ahmadzadeh, Yasmin; Wechsler, Daniel L.; Lyngstad, Torkild Hovde; Rayner, Christopher & Eilertsen, Espen Moen [Show all 9 contributors for this article] (2023). Socioeconomic status and risk for child psychopathology: exploring gene–environment interaction in the presence of gene–environment correlation using extended families in the Norwegian Mother, Father and Child Birth Cohort Study. Journal of Child Psychology and Psychiatry. ISSN 0021-9630. 65(2), p. 176–187. doi: 10.1111/jcpp.13872. Full text in Research Archive Show summary

  Background Low socioeconomic status (SES) is associated with increased risk for emotional and behavioural problems among children. Evidence from twin studies has shown that family SES moderates genetic and environmental influences on child mental health. However, it is also known that SES is itself under genetic influence and previous gene–environment interaction (G×E) studies have not incorporated the potential genetic overlap between child mental health and family SES into G×E analyses. We applied a novel approach using extended family data to investigate the moderation of aetiological influences on child emotional and behavioural problems by parental socioeconomic status in the presence of modelled gene–environment correlation. Methods The sample comprised >28,100 children in extended-family units drawn from the Norwegian Mother, Father and Child Cohort Study (MoBa). Mothers reported children's emotional and behavioural symptoms. Parents' income and educational attainment were obtained through linkage to administrative register data. Bivariate moderation Multiple-Children-of-Twins-and-Siblings (MCoTS) models were used to analyse relationships between offspring outcomes (emotional and behavioural symptom scores) and parental socioeconomic moderators (income rank and educational attainment). Results The aetiology of child emotional symptoms was moderated by maternal and paternal educational attainment. Shared environmental influences on child emotional symptoms were greater at lower levels of parents' education. The aetiology of child behavioural symptoms was moderated by maternal, but not paternal, socioeconomic factors. Genetic factors shared between maternal income and child behavioural symptoms were greater in families with lower levels maternal income. Nonshared environmental influences on child behavioural symptoms were greater in families with higher maternal income and education. Conclusions Parental socioeconomic indicators moderated familial influences and nonshared environmental influences on child emotional and behavioural outcomes. Maternal SES and child mental health share aetiological overlap such that shared genetic influence was greater at the lower end of the socioeconomic distribution. Our findings collectively highlight the role that family socioeconomic factors play in shaping the origins of child emotional and behavioural problems.

• Harris, Gerd Marie Eskerud; Wood, Mollie; Ystrøm, Eivind & Nordeng, Hedvig Marie Egeland (2022). Association of Maternal Use of Triptans during Pregnancy with Risk of Attention-Deficit/Hyperactivity Disorder in Offspring. JAMA Network Open. 5(6). doi: 10.1001/jamanetworkopen.2022.15333. Full text in Research Archive Show summary

  Importance Triptans are commonly used in the treatment of migraine. Prenatal exposure to triptans may be associated with adverse fetal neurodevelopment; however, there is limited information about the long-term safety of triptan use during pregnancy. Objective To examine the association between maternal use of triptans during pregnancy and diagnosis and symptoms of attention-deficit/hyperactivity disorder (ADHD) among offspring. Design, Setting, and Participants This study used data from the Norwegian Mother, Father and Child Cohort Study (recruitment 1999-2008), linked to national health registries. Live-born singleton children born to women with migraine before or during pregnancy were included. Two analytic samples were defined: one to assess ADHD diagnosis and one to assess ADHD symptoms. Data were analyzed from May 1 to November 30, 2021. Exposure Maternal self-report of triptan use during pregnancy. Exposed children were compared with 2 groups of unexposed children whose mothers reported migraine (1) during pregnancy and (2) before pregnancy only. Main Outcomes and Measures An ADHD diagnosis was defined as diagnosis of hyperkinetic disorder or receipt of dispensed ADHD medication. Symptoms of ADHD at 5 years were measured by the Conners’ Parent Rating Scale, where a higher score indicates more symptoms of ADHD. Cox proportional hazards regression models and generalized linear models with inverse probability weights were used to estimate weighted hazard ratios (HRs) and standardized mean differences, respectively, with 95% CIs. Results The ADHD diagnosis sample comprised 10 167 children (mean [SD] maternal age, 30.2 [4.6] years; 5231 boys [51.5%]), and the ADHD symptoms sample comprised 4367 children (mean [SD] maternal age, 30.6 [4.4] years; 2191 boys [50.2%]). Children were followed up for a mean (SD) of 10.6 (2.2) years. Children with prenatal triptan exposure had no increased risk of ADHD diagnosis compared with unexposed children whose mothers had migraine during pregnancy (weighted HR, 1.16; 95% CI, 0.78-1.74) and compared with unexposed children whose mothers had migraine only before pregnancy (weighted HR, 1.28; 95% CI, 0.84-1.94). There were no differences in ADHD symptom scores between exposed and unexposed children. Conclusions and Relevance The findings of this study suggest that there is no increased risk of ADHD among offspring associated with prenatal exposure to triptans.

• Grzeskowiak, Luke E.; Saha, Moni R.; Nordeng, Hedvig Marie Egeland; Ystrøm, Eivind & Amir, Lisa H. (2022). Perinatal antidepressant use and breastfeeding outcomes: Findings from the Norwegian Mother, Father and Child Cohort Study. Acta Obstetricia et Gynecologica Scandinavica. ISSN 0001-6349. 101(3), p. 344–354. doi: 10.1111/aogs.14324. Full text in Research Archive Show summary

  Introduction Antidepressant use is common in the perinatal period, but there are concerns that it can negatively impact on breastfeeding outcomes. The aim of this study was to examine the effects of perinatal antidepressant use on breastfeeding initiation and duration. Material and methods This was a retrospective analysis of 80 882 mother–infant dyads in the Norwegian Mother, Father and Child Cohort Study (MoBa). Women were first classified according to self-reported mental disorders and timing of antidepressant use before and/or after gestational week 28 (i.e., early-mid–gestation and/or late-gestation use). We subsequently classified women according to self-reported mental disorders and antidepressant use postpartum and whether antidepressants were continued from late gestation or were new/restarted. Breastfeeding outcomes included breastfeeding initiation as well as predominant or any breastfeeding and abrupt breastfeeding discontinuation until 6 months. Results Late-gestation antidepressant use was associated with a reduced likelihood of breastfeeding initiation (adjusted relative risk [aRR] 0.93; 95% confidence interval [CI] 0.90–0.97) but not predominant (aRR 0.96; 95% CI 0.67–1.39) or any (aRR 1.00; 95% CI 0.93–1.07) breastfeeding at 6 months compared with unexposed women with mental disorders. When examined according to postnatal antidepressant use, no differences in predominant (aRR 0.94; 95% CI 0.60–1.48) or any breastfeeding (aRR 0.99; 95% CI 0.91–1.07) at 6 months were evident among women who continued antidepressant use from late gestation into the postpartum period compared with unexposed women with mental disorders. In contrast, new/restarted antidepressant use postpartum was associated with a reduced likelihood of predominant (aRR 0.37; 95% CI 0.22–0.61) and any (aRR 0.49; 95% CI 0.42–0.56) breastfeeding at 6 months, as well as increased risk of abrupt breastfeeding discontinuation (aRR 2.64; 95% CI 2.07–3.37) compared with the unexposed women with mental disorders. Conclusions A complex relation exists between depression, antidepressant use, and breastfeeding outcomes. Antidepressant use in late pregnancy was associated with a reduced likelihood of breastfeeding initiation but not breastfeeding duration or exclusivity. In contrast, initiating or restarting antidepressants postpartum was associated with poorer breastfeeding outcomes. Overall, women taking antidepressants and women with a mental disorder may benefit from additional education and support to improve breastfeeding rates and promote maternal and infant health and wellbeing.

• Lund, Ingunn Olea & Ystrøm, Eivind (2022). Prenatal alcohol exposure and child sleep problems: A family-based quasi-experimental study. JCPP Advances. 2(4). doi: 10.1002/jcv2.12111. Full text in Research Archive Show summary

  Background We examine whether associations between prenatal exposure to hazardous maternal alcohol consumption during the first trimester of pregnancy and sleep problems in young children represent a causal association. Methods The population-based sample consists of 15,911 mothers with 30,395 offspring from the Norwegian Mother, Father, and Child Cohort Study (MoBa) and the Medical Birth Registry of Norway (MBRN). Women self-reported pre-pregnancy alcohol consumption and consumption during the first trimester of pregnancy twice: at gestational weeks 17 and 30. Mothers reported their children's sleep problems, when they were 1.5 and 3 years (mean = 50; SD = 10). We tested models adjusting for (1) measured confounders, (2) unmeasured familial risk factors by sibling design, and (3) maternal hazardous drinking in the 3 months prior to pregnancy as an instrumental variable within the sibling design. Results Children of mothers with hazardous drinking during the first trimester were at increased risk of sleep problems at 1.5 (β = 1.14, 95%CI 0.04–2.25) and 3 (β = 2.86, 95%CI 1.85–3.87) years of age. These associations were reduced to close to zero and non-significant at 1.5 (β = −0.32, 95%CI −1.91–1.26) and 3 (β = 0.06, 95%CI −1.56–1.64) years when controlling for both familial and measured environmental risk factors. Conclusions There is a moderate association between maternal hazardous drinking during pregnancy and offspring sleep problems up to age three. This association is explained by risk factors differing between families and does not reflect a cause-effect relationship.

• Eftedal, Nikolai Haahjem; Kleppestø, Thomas Haarklau; Czajkowski, Nikolai Olavi; Sheehy-Skeffington, Jennifer; Røysamb, Espen & Vassend, Olav Mandt [Show all 8 contributors for this article] (2022). Justice sensitivity is undergirded by separate heritable motivations to be morally principled and opportunistic. Scientific Reports. 12. doi: 10.1038/s41598-022-09253-2. Full text in Research Archive Show summary

  Abstract Injustice typically involves some people benefitting at the expense of others. An opportunist might then be selectively motivated to amend only the injustice that is harmful to them, while someone more principled would respond consistently regardless of whether they stand to gain or lose. Here, we disentangle such principled and opportunistic motives towards injustice. With a sample of 312 monozygotic- and 298 dizygotic twin pairs (N = 1220), we measured people’s propensity to perceive injustice as victims, observers, beneficiaries, and perpetrators of injustice, using the Justice Sensitivity scale. With a biometric approach to factor analysis, that provides increased stringency in inferring latent psychological traits, we find evidence for two substantially heritable factors explaining correlations between Justice Sensitivity facets. We interpret these factors as principled justice sensitivity (h 2  = 0.45) leading to increased sensitivity to injustices of all categories, and opportunistic justice sensitivity (h 2  = 0.69) associated with increased sensitivity to being a victim and a decreased propensity to see oneself as a perpetrator. These novel latent constructs share genetic substrate with psychological characteristics that sustain broad coordination strategies that capture the dynamic tension between honest cooperation versus dominance and defection, namely altruism, interpersonal trust, agreeableness, Social Dominance Orientation and opposition to immigration and foreign aid.

• Bjørndal, Ludvig Daae; Kendler, Kenneth S.; Reichborn-Kjennerud, Ted & Ystrøm, Eivind (2022). Stressful life events increase the risk of major depressive episodes: A population-based twin study. Psychological Medicine. ISSN 0033-2917. 53(11), p. 5194–5202. doi: 10.1017/S0033291722002227. Full text in Research Archive Show summary

  Background Previous studies have found that stressful life events (SLEs) are associated with an increased risk of adult depression. However, many studies are observational in nature and limited by methodological issues, such as potential confounding by genetic factors. Genetically informative research, such as the co-twin control design, can strengthen causal inference in observational studies. Discrete-time survival analysis has several benefits and multilevel survival analysis can incorporate frailty terms (random effects) to estimate the components of the biometric model. In the current study, we investigated associations between SLEs and depression risk in a population-based twin sample (N = 2299). Methods A co-twin control design was used to investigate the influence of the occurrence of SLEs on depression risk. The co-twin control design involves comparing patterns of associations in the full sample and within dizygotic (DZ) and monozygotic twins (MZ). Associations were modelled using discrete-time survival analysis with biometric frailty terms. Data from two time points were used in the analyses. Mean age at Wave 1 was 28 years and mean age at Wave 2 was 38 years. Results SLE occurrence was associated with increased depression risk. Co-twin control analyses indicated that this association was at least in part due to the causal influence of SLE exposure on depression risk for event occurrence across all SLEs and for violent SLEs. A minor proportion of the total genetic risk of depression reflected genetic effects related to SLEs. Conclusions The results support previous research in implicating SLEs as important risk factors with probable causal influence on depression risk.

• Ystrøm, Eivind; Degerud, Eirik Magnus Meek; Tesli, Martin Steen; Høye, Anne; Reichborn-Kjennerud, Ted & Næss, Øyvind Erik (2022). Alcohol consumption and lower risk of cardiovascular and all-cause mortality: The impact of accounting for familial factors in twins. Psychological Medicine. ISSN 0033-2917. doi: 10.1017/S0033291722000812. Full text in Research Archive Show summary

  Background. A moderate to high alcohol consumption is associated with a lower risk of cardiovascular disease (CVD) mortality in comparison with low consumption. The mechanisms underlying this association are not clear and have been suggested to be caused by residual confounding. The main objective of this study was to separate the familial and individual risk for CVD mortality and all-cause mortality related to alcohol consumption. This will be done by estimating the risk for CVD mortality and all-cause mortality in twin pairs discordant for alcohol consumption.<p> <p>Methods. Alcohol consumption was assessed at two time points using self-report questionnaires in the Norwegian Twin Registry. Data on CVD mortality was obtained from the Norwegian Cause of Death Registry. Exposure–outcome associations for all-cause mortality and mortality due to other causes than CVD were estimated for comparison. <p>Results. Coming from a family with moderate to high alcohol consumption was protective against cardiovascular death (HR = 0.54, 95% CI 0.65–0.83). Moderate and high alcohol consumption levels were associated with a slightly increased risk of CVD mortality at the individual level (HR = 1.33, 95% CI 1.02–1.73). There was no association between alcohol consumption and all-cause mortality both at the familial nor at the individual level. <p>Conclusions. The protective association of moderate to high alcohol consumption with a lower risk of CVD mortality was accounted for by familial factors in this study of twins. Early life genetic and environmental familial factors may mask an absence of health effect of moderate to high alcohol consumption on cardiovascular mortality.

• Lund, Ingunn Olea; Andersen, Njål; Handal, Marte; Ask, Helga; Skurtveit, Svetlana Ondrasova & Ystrøm, Eivind [Show all 7 contributors for this article] (2022). Parental drinking, mental health and education, and extent of offspring’s healthcare utilisation for anxiety/depression: A HUNT survey and registry study. Scandinavian Journal of Public Health. ISSN 1403-4948. p. 1–9. doi: 10.1177/14034948221076212. Full text in Research Archive Show summary

  Aims: Certain risk constellations of parental drinking, mental health and years of education are prospectively associated with offspring’s risk for a diagnosis of anxiety/depression, but it remains unknown how they may relate to other aspects of offspring’s mental health. We examined whether such risk constellations were also prospectively associated with the extent of offspring’s utilisation of healthcare services for anxiety/depression. Methods: The sample included 8773 adolescent offspring of 6696 two-parent families who participated in the Nord-Trøndelag Health Study in Norway. The exposures consisted of five parental risk constellations characterised by drinking frequencies and quantities, years of education and mental health previously derived based on the parental self-reports using latent profile analysis. The outcomes were the number of years in contact, and the total number of consultations/visits, with healthcare services for anxiety/depression in adolescents and young adults as recorded in healthcare registries in the period 2008–2014. Associations were examined using zero-inflated negative binomial regression models, accounting for demographics and offspring’s early mental health. Results: Parental risk constellations were not significantly associated with the extent of offspring’s healthcare utilisation for anxiety/depression during the seven-year study period, neither in respect of number of years nor in number of contacts. Conclusions: Offspring of four risky constellations were no more likely to use healthcare services for longer time periods or have more consultations/visits than offspring of the lowest-risk constellation. Parental risk constellations appear more informative for understanding disorder aetiology than for understanding management and treatment of anxiety and depression during adolescence and early adulthood.

• Cheesman, Rosa Catherine Gillespie; Borgen, Nicolai T.; Lyngstad, Torkild Hovde; Eilertsen, Espen Moen; Ayorech, Ziada & Torvik, Fartein Ask [Show all 9 contributors for this article] (2022). A population-wide gene-environment interaction study on how genes, schools, and residential areas shape achievement. npj Science of learning. Full text in Research Archive
• Cheesman, Rosa Catherine Gillespie; Borgen, Nicolai Topstad; Lyngstad, Torkild Hovde; Eilertsen, Espen Moen; Ayorech, Ziada & Torvik, Fartein Ask [Show all 9 contributors for this article] (2022). A population-wide gene-environment interaction study on how genes, schools, and residential areas shape achievement. npj Science of learning. 7, p. 1–9. doi: 10.1038/s41539-022-00145-8. Full text in Research Archive Show summary

  Abstract A child’s environment is thought to be composed of different levels that interact with their individual genetic propensities. However, studies have not tested this theory comprehensively across multiple environmental levels. Here, we quantify the contributions of child, parent, school, neighbourhood, district, and municipality factors to achievement, and investigate interactions between polygenic indices for educational attainment (EA-PGI) and environmental levels. We link population-wide administrative data on children’s standardised test results, schools and residential identifiers to the Norwegian Mother, Father, and Child Cohort Study (MoBa), which includes &gt;23,000 genotyped parent-child trios. We test for gene-environment interactions using multilevel models with interactions between EA-PGI and random effects for school and residential environments (thus remaining agnostic to specific features of environments). We use parent EA-PGI to control for gene-environment correlation. We found an interaction between students’ EA-PGI and schools suggesting compensation: higher-performing schools can raise overall achievement without leaving children with lower EA-PGI behind. Differences between schools matter more for students with lower EA-PGI, explaining 4 versus 2% of the variance in achievement for students 2 SD below versus 2 SD above the mean EA-PGI. Neighbourhood, district, and municipality variation contribute little to achievement (&lt;2% of the variance collectively), and do not interact with children’s individual EA-PGI. Policy to reduce social inequality in achievement in Norway should focus on tackling unequal support across schools for children with difficulties.

• Isungset, Martin Arstad; Conley, Dalton C; Zachrisson, Henrik Daae; Ystrøm, Eivind; Havdahl, Alexandra & Njølstad, Pål Rasmus [Show all 7 contributors for this article] (2022). Social and genetic associations with educational performance in a Scandinavian welfare state. Proceedings of the National Academy of Sciences of the United States of America (PNAS). ISSN 0027-8424. 119(25). doi: 10.1073/pnas.2201869119. Full text in Research Archive Show summary

  Recent research has suggested that across Western developed societies, the influence of genetics on educational outcomes is relatively constant. However, the degree to which family environment matters varies, such that countries with high levels of intergenerational mobility have weaker associations of family background. Research in this vein has relied on twin-based estimates, which involve variance decomposition, so direct assessment of the association of genes and environments is not possible. In the present study, we approach the question by directly measuring the impact of child genotype, parental genetic nurture, and parental realized education on educational achievement in primary and secondary school. We deploy data from a social democratic context (Norway) and contrast our findings with those derived from more liberal welfare state contexts. Results point to genetics only confounding the relationship between parent status and offspring achievement to a small degree. Genetic nurture associations are similar to those in other societies. We find no, or very small, gene–environment interactions and parent–child genotype interactions with respect to test scores. In sum, in a Scandinavian welfare state context, both genetic and environmental associations are of similar magnitude as in societies with less-robust efforts to mitigate the influence of family background.

• Tesli, Martin Steen; Degerud, Eirik Magnus Meek; Plana-Ripoll, Oleguer; Gustavson, Kristin; Torvik, Fartein Ask & Ystrøm, Eivind [Show all 13 contributors for this article] (2022). Educational attainment and mortality in schizophrenia. Acta Psychiatrica Scandinavica. ISSN 0001-690X. 145(5), p. 481–493. doi: 10.1111/acps.13407. Full text in Research Archive Show summary

  Background Individuals suffering from schizophrenia have a reduced life expectancy with cardiovascular disease (CVD) as a major contributor. Low educational attainment is associated with schizophrenia, as well as with all-cause and CVD mortality. However, it is unknown to what extent low educational attainment can explain the increased mortality in individuals with schizophrenia. Aim Here, we quantify associations between educational attainment and all-cause and CVD mortality in individuals with schizophrenia, and compare them with the corresponding associations in the general population. Method All Norwegian citizens born between January 1, 1925, and December 31, 1959, were followed up from January 1, 1990, to December 31, 2014. The total sample included 1,852,113 individuals, of which 6548 were registered with schizophrenia. We estimated hazard ratios (HR) for all-cause and CVD mortality with Cox models, in addition to life years lost. Educational attainment for index persons and their parents were included in the models. Results In the general population individuals with low educational attainment had higher risk of all-cause (HR: 1.48 [95% CI: 1.47–1.49]) and CVD (HR: 1.59 [95% CI: 1.57–1.61]) mortality. In individuals with schizophrenia these estimates were substantially lower (all-cause: HR: 1.13 [95% CI: 1.05–1.21] and CVD: HR: 1.12 [95% CI: 0.98–1.27]). Low educational attainment accounted for 3.28 (3.21–3.35) life years lost in males and 2.48 (2.42–2.55) years in females in the general population, but was not significantly associated with life years lost in individuals with schizophrenia. Results were similar for parental educational attainment. Conclusions Our results indicate that while individuals with schizophrenia in general have lower educational attainment and higher mortality rates compared with the general population, the association between educational attainment and mortality is smaller in schizophrenia subjects than in the general population.

• Jami, Eshim S.; Hammerschlag, Anke R.; Ip, Hill F.; Allegrini, Andrea G.; Benyamin, Beben & Border, Richard [Show all 94 contributors for this article] (2022). Genome-wide association meta-analysis of childhood and adolescent internalizing symptoms. Journal of the American Academy of Child and Adolescent Psychiatry. ISSN 0890-8567. 61(7), p. 934–945. doi: 10.1016/j.jaac.2021.11.035. Full text in Research Archive Show summary

  Objective: To investigate the genetic architecture of internalizing symptoms in childhood and adolescence. Method: In 22 cohorts, multiple univariate genome-wide association studies (GWASs) were performed using repeated assessments of internalizing symptoms, in a total of 64,561 children and adolescents between 3 and 18 years of age. Results were aggregated in meta-analyses that accounted for sample overlap, first using all available data, and then using subsets of measurements grouped by rater, age, and instrument. Results: The meta-analysis of overall internalizing symptoms (INToverall) detected no genome-wide significant hits and showed low single nucleotide polymorphism (SNP) heritability (1.66%, 95% CI = 0.84-2.48%, neffective = 132,260). Stratified analyses indicated rater-based heterogeneity in genetic effects, with self-reported internalizing symptoms showing the highest heritability (5.63%, 95% CI = 3.08%-8.18%). The contribution of additive genetic effects on internalizing symptoms appeared to be stable over age, with overlapping estimates of SNP heritability from early childhood to adolescence. Genetic correlations were observed with adult anxiety, depression, and the well-being spectrum (|rg| > 0.70), as well as with insomnia, loneliness, attention-deficit/hyperactivity disorder, autism, and childhood aggression (range |rg| = 0.42-0.60), whereas there were no robust associations with schizophrenia, bipolar disorder, obsessive-compulsive disorder, or anorexia nervosa. Conclusion: Genetic correlations indicate that childhood and adolescent internalizing symptoms share substantial genetic vulnerabilities with adult internalizing disorders and other childhood psychiatric traits, which could partially explain both the persistence of internalizing symptoms over time and the high comorbidity among childhood psychiatric traits. Reducing phenotypic heterogeneity in childhood samples will be key in paving the way to future GWAS success.

• Widding-Havneraas, Tarjei; Markussen, Simen; Elwert, Felix; Lyhmann, Ingvild; Bjelland, Ingvar & Halmøy, Anne [Show all 10 contributors for this article] (2022). Geographical variation in ADHD: do diagnoses reflect symptom levels? European Child and Adolescent Psychiatry. ISSN 1018-8827. 32. doi: 10.1007/s00787-022-01996-7. Full text in Research Archive Show summary

  Rates of ADHD diagnosis vary across regions in many countries. However, no prior study has investigated how much within-country geographic variation in ADHD diagnoses is explained by variation in ADHD symptom levels. We examine whether ADHD symptom levels explain variation in ADHD diagnoses among children and adolescents using nationwide survey and register data in Norway. Geographical variation in incidence of ADHD diagnosis was measured using Norwegian registry data from the child and adolescent mental health services for 2011–2016. Geographical variation in ADHD symptom levels in clinics’ catchment areas was measured using data from the Norwegian mother, father and child cohort study for 2011–2016 (n = 39,850). Cross-sectional associations between ADHD symptom levels and the incidence of ADHD diagnoses were assessed with fractional response models. Geographical variation in ADHD diagnosis rates is much larger than what can be explained by geographical variation in ADHD symptoms levels. Treatment in the Norwegian child and adolescent mental health services is free, universally available upon referral, and practically without competition from the private sector. Factors beyond health care access and unequal symptom levels seem responsible for the geographical variation in ADHD diagnosis.

• Pingault, Jean-Baptiste; Barkhuizen, Wikus; Wang, Biyao; Hannigan, Laurie John; Eilertsen, Espen Moen & Corfield, Elizabeth Claire [Show all 16 contributors for this article] (2022). Genetic nurture versus genetic transmission of risk for ADHD traits in the Norwegian Mother, Father and Child Cohort Study. Molecular Psychiatry. ISSN 1359-4184. doi: 10.1038/s41380-022-01863-6. Full text in Research Archive Show summary

  Identifying mechanisms underlying the intergenerational transmission of risk for attention-deficit/hyperactivity disorder (ADHD) traits can inform interventions and provide insights into the role of parents in shaping their children’s outcomes. We investigated whether genetic transmission and genetic nurture (environmentally mediated effects) underlie associations between polygenic scores indexing parental risk and protective factors and their offspring’s ADHD traits. This birth cohort study included 19,506 genotyped mother-father-offspring trios from the Norwegian Mother, Father and Child Cohort Study. Polygenic scores were calculated for parental factors previously associated with ADHD, including psychopathology, substance use, neuroticism, educational attainment, and cognitive performance. Mothers reported on their 8-year-old children’s ADHD traits (n = 9,454 children) using the Parent/Teacher Rating Scale for Disruptive Behaviour Disorders. We found that associations between ADHD maternal and paternal polygenic scores and child ADHD traits decreased significantly when adjusting for the child polygenic score (pΔβ = 9.95 × 10−17 for maternal and pΔβ = 1.48 × 10−14 for paternal estimates), suggesting genetic transmission of ADHD risk. Similar patterns suggesting genetic transmission of risk were observed for smoking, educational attainment, and cognition. The maternal polygenic score for neuroticism remained associated with children’s ADHD ratings even after adjusting for the child polygenic score, indicating genetic nurture. There was no robust evidence of genetic nurture for other parental factors. Our findings indicate that the intergenerational transmission of risk for ADHD traits is largely explained by the transmission of genetic variants from parents to offspring rather than by genetic nurture. Observational associations between parental factors and childhood ADHD outcomes should not be interpreted as evidence for predominantly environmentally mediated effects.

• Baier, Tina; Eilertsen, Espen Moen; Ystrøm, Eivind; Zambrana, Imac Maria & Lyngstad, Torkild Hovde (2022). An anatomy of the intergenerational correlation of educational attainment – Learning from the educational attainments of Norwegian twins and their children. Research in Social Stratification and Mobility. ISSN 0276-5624. 79. doi: 10.1016/j.rssm.2022.100691. Full text in Research Archive Show summary

  Research on the intergenerational correlation of educational attainment (ICE) has long attempted to identify the impact of family background, specifically parent’s education. However, previous research has largely ignored genetic inheritance. We address this shortcoming by adopting a Multiple-Children-of-Twin design and decompose the ICE into its environmental and genetic transmission mechanisms. This decomposition reveals to what extent the impact of parents’ education operates through the rearing context and/or genetic factors. We use a register-based dataset from Norway, a context with egalitarian access to education. Our results show that the direct impact of parents’ education is negligible once genetic factors are accounted for. While genetic factors represent the main driver of the ICE, the genetic variants that mattered for educational attainment in the parent generation overlap only partially with those that mattered for their offspring’s attainment. Together, our findings complement common sociological narratives on how parent’s education affects offspring’s education by emphasizing the role of genetic transmission. Furthermore, our study challenges current research practices in genetics that overlook the importance of parallel changes in social structures and gene-expression over generations.

• Walle, Kjersti Mæhlum; Askeland, Ragna Bugge; Gustavson, Kristin; Mjaaland, Siri; Ystrøm, Eivind & Lipkin, W. Ian [Show all 13 contributors for this article] (2022). Risk of attention-deficit hyperactivity disorder in offspring of mothers with infections during pregnancy. JCPP Advances. 2(2), p. 1–11. doi: 10.1002/jcv2.12070. Full text in Research Archive Show summary

  Background Maternal infections during pregnancy are common events that have been suggested to be risk factors for Attention-deficit hyperactivity disorder (ADHD) in offspring. Only a few studies have been conducted to date and results are conflicting. The current study investigates the associations between specific groups of prenatal maternal infections and offspring ADHD, considering timing of exposure and the role of fever. Methods We used data from the prospective Norwegian Mother, Father and Child Cohort Study (MoBa), including more than 112,000 pregnancies, linked with data from the Medical Birth Registry of Norway and the Norwegian Patient Registry to estimate odds ratios for the likelihood that children develop ADHD after being exposed to maternal infections during gestation. Results Children exposed to any maternal infection during pregnancy showed increased risk of receiving an ADHD diagnosis (OR = 1.15, CI = 1.03–1.27). Specifically, increased ADHD risk was observed after exposure to genitourinary infections in second (OR = 1.42, CI = 1.06–1.90) or third trimester (OR = 2.04, CI = 1.19–3.49), and to respiratory infections in second trimester (OR = 1.31, CI = 1.12–1.54), provided these infections were accompanied by episodes of fever. Increased ADHD risk was also observed after exposure to diarrhea without fever in the third trimester (OR = 1.25, CI = 1.07–1.46). Conclusions Overall, our results suggest that prenatal exposure to maternal infections, particularly with co-occurring episodes of fever, are risk factors for ADHD. Fever (or severity of the infection) appears to be more important in mid-pregnancy associations. Our results indicate that type of infection and timing of exposure might influence the associations, but small effect sizes require careful interpretations. The association between infection and ADHD should be estimated using discordant siblings or other negative control designs that give better adjustment for unmeasured familial confounding.

• Trønnes, Johanne Naper; Lupattelli, Angela; Ystrøm, Eivind & Nordeng, Hedvig Marie Egeland (2022). Analysis of Prenatal Exposure to Opioid Analgesics and Scholastic Skills in Children in Fifth Grade in Norway. JAMA Network Open. 5(7). doi: 10.1001/jamanetworkopen.2022.22425. Full text in Research Archive Show summary

  Importance Few studies have examined the neurodevelopmental consequences of prenatal exposure to opioid analgesics. Therefore, it is necessary to gain knowledge to inform clinical decisions for pregnant women with moderate to severe pain. Objective To investigate fifth-grade scholastic skills in children with prenatal exposure to opioid analgesics. Design, Setting, and Participants A cohort study was conducted based on data from the Norwegian Mother, Father, and Child Cohort (1999-2008). These data were linked to the Medical Birth Registry of Norway, and data from Statistics Norway included 64 256 live-born singletons, born to 54 568 mothers who reported pain during pregnancy, were analyzed. The study was conducted from July 1 to December 15, 2021. Exposures Self-reported exposure to opioid analgesics during pregnancy, characterized in terms of any exposure, the exposure timing, and the exposure duration. Main Outcomes and Measures Scores from 3 national tests for children in fifth grade. The tests measured scholastic skills in literacy, numeracy, and the English language. Test scores were standardized to z scores. Differences in z scores were compared between children of mothers exposed to opioid analgesics during pregnancy and children of mothers with only prepregnancy opioid exposure. Results Of the 64 256 children included, 32 521 were boys (50.6%), and 1483 children (2.3%) were exposed to an opioid analgesic at least once during gestation. All test scores were similar between children with any exposure to opioid analgesics in utero and children with only prepregnancy exposure. Children exposed in the first trimester and those exposed in two or three 4-week intervals during pregnancy scored lower than children of mothers with only prepregnancy exposures on tests in literacy (weighted β [wβ], −0.13; 95% CI, −0.25 to −0.01 and wβ, −0.19; 95% CI, −0.35 to −0.04) and numeracy (wβ, −0.14; 95% CI, −0.25 to −0.04 and wβ, −0.19; 95% CI, −0.34 to −0.05). These differences were small and may not be clinically relevant. Conclusions and Relevance In this large birth cohort, prenatal exposure to opioid analgesics had no substantial negative association with fifth-grade scholastic skills. However, adequate pain management in pregnancy may be addressed on an individual patient level, bearing in mind the benefits and risks of different analgesic therapies.

• Løke, Daniel; Løvstad, Marianne; Andelic, Nada; Andersson, Stein; Ystrøm, Eivind & Vassend, Olav Mandt (2022). The role of pain and psychological distress in fatigue: a co-twin and within-person analysis of confounding and causal relations. Health Psychology and Behavioral Medicine. 10(1), p. 160–179. doi: 10.1080/21642850.2022.2033121. Full text in Research Archive Show summary

  Objective: Fatigue is a common symptom in somatic and mental illness. Musculoskeletal pain and psychological distress have in turn frequently been shown to be associated with fatigue across clinical conditions and in the general population. The study aims to disentangle direct effects from those due to mere confounding from shared etiologies. Design: The study used genetically informative longitudinal twin data, through a co-twin control design with an additional within-person dimension. Methods: Data on fatigue, pain and distress from 2196 mono – and dizygotic twins from the Norwegian Twin Registry examined at two time points five years apart was analyzed using multilevel generalized linear regression modeling. Fatigue was regressed on pain and distress, with further controls added for confounding from genetic and stable non-shared environmental sources. Results: Pain and distress had a significant impact on fatigue at genetic, stable non-shared environmental and time-varying levels, even when controlling for somatic comorbidity. Conclusion: The findings indicate that a significant proportion of the association between fatigue, pain and distress is due to genetic and environmental confounding. Pain and distress exert significant, albeit smaller effects on fatigue even when controlling for genetic and stable environmental contributions, indicating direct effects. Potential etiological pathways and underlying mechanisms are discussed.

• Torvik, Fartein Ask; Eilertsen, Espen Moen; Hannigan, Laurie John; Cheesman, Rosa Catherine Gillespie; Howe, Laurence J. & Magnus, Per Minor [Show all 11 contributors for this article] (2022). Modeling assortative mating and genetic similarities between partners, siblings, and in-laws. Nature Communications. 13(1). doi: 10.1038/s41467-022-28774-y. Full text in Research Archive Show summary

  Assortative mating on heritable traits can have implications for the genetic resemblance between siblings and in-laws in succeeding generations. We studied polygenic scores and phenotypic data from pairs of partners (n = 26,681), siblings (n = 2,170), siblings-in-law (n = 3,905), and co-siblings-in-law (n = 1,763) in the Norwegian Mother, Father and Child Cohort Study. Using structural equation models, we estimated associations between measurement error-free latent genetic and phenotypic variables. We found evidence of genetic similarity between partners for educational attainment (rg = 0.37), height (rg = 0.13), and depression (rg = 0.08). Common genetic variants associated with educational attainment correlated between siblings above 0.50 (rg = 0.68) and between siblings-in-law (rg = 0.25) and co-siblings-in-law (rg = 0.09). Indirect assortment on secondary traits accounted for partner similarity in education and depression, but not in height. Comparisons between the genetic similarities of partners and siblings indicated that genetic variances were in intergenerational equilibrium. This study shows genetic similarities between extended family members and that assortative mating has taken place for several generations.

• Cheesman, Rosa Catherine Gillespie; Eilertsen, Espen Moen; Ayorech, Ziada; Borgen, Nicolai Topstad; Andreassen, Ole & Larsson, Henrik [Show all 9 contributors for this article] (2022). How interactions between ADHD and schools affect educational achievement: a family-based genetically sensitive study. Journal of Child Psychology and Psychiatry. ISSN 0021-9630. 63(10), p. 1174–1185. doi: 10.1111/jcpp.13656. Full text in Research Archive Show summary

  Background Children with ADHD tend to achieve less than their peers in school. It is unknown whether schools moderate this association. Nonrandom selection of children into schools related to variations in their ADHD risk poses a methodological problem. Methods We linked data on ADHD symptoms of inattention and hyperactivity and parent–child ADHD polygenic scores (PGS) from the Norwegian Mother, Father, and Child Cohort Study (MoBa) to achievement in standardised tests and school identifiers. We estimated interactions of schools with individual differences between students in inattention, hyperactivity, and ADHD-PGS using multilevel models with random slopes for ADHD effects on achievement over schools. In our PGS analyses, we adjust for parental selection of schools by adjusting for parental ADHD-PGS (a within-family PGS design). We then tested whether five school sociodemographic measures explained any interactions. Results Analysis of up to 23,598 students attending 2,579 schools revealed interactions between school and ADHD effects on achievement. The variability between schools in the effects of inattention, hyperactivity and within-family ADHD-PGS on achievement was 0.08, 0.07 and 0.05 SDs, respectively. For example, the average effect of inattention on achievement was β = −0.23 (SE = 0.009), but in 2.5% of schools with the weakest effects, the value was −0.07 or less. ADHD has a weaker effect on achievement in higher-performing schools. Schools make more of a difference to the achievements of students with higher levels of ADHD, explaining over four times as much variance in achievement for those with high versus average inattention symptoms. School sociodemographic measures could not explain the ADHD-by-school interactions. Conclusions Although ADHD symptoms and genetic risk tend to hinder achievement, schools where their effects are weaker do exist. Differences between schools in support for children with ADHD should be evened out.

• Eilertsen, Espen Moen; Cheesman, Rosa Catherine Gillespie; Ayorech, Ziada; Røysamb, Espen; Pingault, Jean-Baptiste & Njølstad, Pål Rasmus [Show all 11 contributors for this article] (2022). On the importance of parenting in externalizing disorders: an evaluation of indirect genetic effects in families. Journal of Child Psychology and Psychiatry. ISSN 0021-9630. 63(10), p. 1186–1195. doi: 10.1111/jcpp.13654. Full text in Research Archive Show summary

  Background: Theoretical models of the development of childhood externalizing disorders emphasize the role of parents. Empirical studies have not been able to identify specific aspects of parental behaviors explaining a considerable proportion of the observed individual differences in externalizing problems. The problem is complicated by the contribution of genetic factors to externalizing problems, as parents provide both genes and environments to their children. We studied the joint contributions of direct genetic effects of children and the indirect genetic effects of parents through the environment on externalizing problems. Methods: The study used genome-wide single nucleotide polymorphism data from 9,675 parent–offspring trios participating in the Norwegian Mother Father and child cohort study. Based on genomic relatedness matrices, we estimated the contribution of direct genetic effects and indirect maternal and paternal genetic effects on ADHD, conduct and disruptive behaviors at 8 years of age. Results: Models including indirect parental genetic effects were preferred for the ADHD symptoms of inattention and hyperactivity, and conduct problems, but not oppositional defiant behaviors. Direct genetic effects accounted for 11% to 24% of the variance, whereas indirect parental genetic effects accounted for 0% to 16% in ADHD symptoms and conduct problems. The correlation between direct and indirect genetic effects, or gene–environment correlations, decreased the variance with 16% and 13% for conduct and inattention problems, and increased the variance with 6% for hyperactivity problems. Conclusions: This study provides empirical support to the notion that parents have a significant role in the development of childhood externalizing behaviors. The parental contribution to decrease in variation of inattention and conduct problems by gene–environment correlations would limit the number of children reaching clinical ranges in symptoms. Not accounting for indirect parental genetic effects can lead to both positive and negative bias when identifying genetic variants for childhood externalizing behaviors.

• Trønnes, Johanne Naper; Lupattelli, Angela; Handal, Marte; Skurtveit, Svetlana Ondrasova; Ystrom, Eivind & Nordeng, Hedvig Marie Egeland (2021). Association of Timing and Duration of Prenatal Analgesic Opioid Exposure with Attention-Deficit/Hyperactivity Disorder in Children. JAMA Network Open. 4(9), p. 1–14. doi: 10.1001/jamanetworkopen.2021.24324. Full text in Research Archive Show summary

  Importance Prior studies have reported that the use of illicit opioids during pregnancy is associated with increased risk of attention-deficit/hyperactivity disorder (ADHD) in offspring; however, evidence regarding the association of analgesic opioids is limited. Objective To examine the association of timing and duration of prenatal analgesic opioid exposure with ADHD in children. Design, Setting, and Participants This cohort study uses data from the Norwegian Mother, Father and Child Cohort study (1999-2008), a nationwide birth cohort study linked to national health registries, with a mean (SD) follow-up of 10.8 (2.2) years. A total of 73 784 live-born singleton children born to 62 013 mothers who reported a pain-related condition before and/or during pregnancy were included, with 2 comparator groups: (1) mothers who did not use any opioids and (2) mothers who used opioids before pregnancy only. Data were analyzed from June to December 2020. Exposures Maternal self-report of analgesic opioid use during pregnancy, by timing (early and middle and/or late) and duration (≥5 weeks vs ≤4 weeks). Main Outcomes and Measures Diagnosis of ADHD or filled prescription for ADHD medication in children and symptoms of ADHD at child age 5 years, measured by Conners’ Parent Rating Scale–Revised. Inverse probability of treatment weights were used to control for measured confounding. Cox regression was used to estimate hazard ratios (HRs) and 95% CIs. Results The analyses of ADHD diagnosis and ADHD symptoms included 73 480 children (35 996 [49.0%] girls; mean [SD] maternal age, 30.0 [4.6] years) and 31 270 children (15 377 [49.2%] girls; mean [SD] maternal age, 30.5 [4.4] years), respectively. Overall, 1726 children in the ADHD diagnosis sample (2.3%) and 667 children in the ADHD symptom sample (2.1%) were exposed to an analgesic opioid at least once during gestation. No associations between timing of prenatal analgesic opioid exposure and ADHD diagnosis or symptoms was found. Exposure for 5 or more weeks was associated with an increased risk of ADHD diagnosis (HR, 1.60, 95% CI, 1.04-2.47) compared with exposure for 4 weeks or less; however, there was no such association for the risk of ADHD symptoms. Conclusions and Relevance In this cohort study, a slightly elevated risk of ADHD diagnosis after prenatal analgesic opioid exposure for 5 or more weeks was found compared with exposure for 4 weeks or less. This result may be driven by longer duration of use; however, the role of residual or unmeasured confounding cannot be excluded. This finding needs to be replicated in other studies.

• Andersen, Sarah Hjorth; Lupattelli, Angela; Handal, Marte; Spigset, Olav; Ystrøm, Eivind & Nordeng, Hedvig Marie Egeland (2021). Prenatal Exposure to Non-Steroidal Anti-Inflammatory Drugs and Risk of Attention-Deficit/Hyperactivity Disorder - a Follow-Up Study in the Norwegian Mother, Father and Child Cohort. Pharmacoepidemiology and Drug Safety. ISSN 1053-8569. 30(10), p. 1380–1390. doi: 10.1002/pds.5250. Full text in Research Archive Show summary

  Purpose To estimate the association between Attention-Deficit/Hyperactivity Disorder (ADHD) in children in preschool and primary school, and prenatal exposure to non-steroidal anti-inflammatory drugs (NSAIDs) by timing and duration. Methods This study was based on the Norwegian Mother, Father and Child Cohort Study linked to the Medical Birth Registry of Norway, the Norwegian Patient Registry (NPR) and the Norwegian Prescription Database (NorPD). NSAID exposure was identified by maternal self-report in pregnancy. Child diagnosis of ADHD was obtained from NPR and NorPD. Symptoms of ADHD at age 5 years were measured using Conners' Parent Rating Scale-Revised, where higher scores correspond to more symptoms. To account for time-varying exposure and confounders, marginal structural models were fitted to estimate hazard ratios and mean difference in z-scores. Results The analyses on ADHD diagnosis and ADHD symptoms included 56 340 and 34 961 children respectively. Children exposed to NSAIDs prenatally had no increased risk of ADHD diagnosis (first trimester: HR 1.12, 95% CI 0.86;1.45, second trimester: HR 0.98, 95% CI 0.69;1.38, third trimester: HR 0.68, 95% CI 0.31; 1.46) or ADHD symptoms (first trimester: standardized mean difference 0.03, 95% CI −0.03;0.09, second trimester: standardized mean difference 0.03, 95% CI −0.04;0.11, third trimester: standardized mean difference 0.11, 95% CI −0.03; 0.25). There was no duration-response relationship for either outcome. Conclusion Though non-differential misclassification of the exposure may have attenuated results, these findings are reassuring and suggest no substantially increased risk of ADHD diagnosis or symptoms in children prenatally exposed to NSAIDs, regardless of timing or duration.

• Lupattelli, Angela; Mahic, Milada; Handal, Marte; Ystrøm, Eivind; Reichborn-Kjennerud, Ted & Nordeng, Hedvig Marie Egeland (2021). Attention-Deficit/Hyperactivity Disorder in Children Following Prenatal Exposure to Antidepressants: results from the Norwegian Mother, Father and Child Cohort Study. BJOG: An International Journal of Obstetrics and Gynaecology. ISSN 1470-0328. 128(21), p. 1917–1927. doi: 10.1111/1471-0528.16743. Full text in Research Archive Show summary

  Objective To determine the association between child attention-deficit/hyperactivity disorder (ADHD) and prenatal exposure to selective serotonin (SSRI) and serotonin-norepinephrine (SNRI) reuptake inhibitor antidepressants, by timing and duration, with quantification of bias due to exposure misclassification. Design Norwegian Mother, Father and Child Cohort Study and national health registries. Setting Nationwide, Norway. Population A total of 6395 children born to women who reported depression/anxiety in pregnancy and were either medicated with SSRI/SNRI in pregnancy (n = 818) or non-medicated (n = 5228), or did not report depression/anxiety but used antidepressants 6 months before pregnancy (discontinuers, n = 349). Main outcome measure Diagnosis of ADHD or filled prescription for ADHD medication in children, and mother-reported symptoms of ADHD by child age 5 years. Results When the hazard was averaged over the duration of the study follow up, there was no difference in ADHD risk between ever in utero SSRI/SNRI-exposed children and comparators (weighted hazard ratio [wHR] 1.07, 95% CI 0.76–1.51 versus non-medicated; wHR 1.53, 95% CI 0.77–3.07 versus discontinuers). Underestimation of effects due to exposure misclassification was modest. In early childhood, the risk for ADHD was lower with prenatal SSRI/SNRI exposure compared with no exposure, and so were ADHD symptoms (weighted β −0.23, 95% CI −0.39 to −0.08); this risk became elevated at child age 7–9 years (wHR 1.93, 95% CI 1.22–3.05). Maternal depression/anxiety before pregnancy was independently associated with child ADHD. Conclusion Prenatal SSRI/SNRI exposure is unlikely to considerably increase the risk of child ADHD beyond that posed by maternal depression/anxiety. The elevated risk at child age 7–9 years needs to be elucidated.

• Gustavson, Kristin; Torvik, Fartein Ask; Eilertsen, Espen Moen; Ask, Helga; McAdams, Tom A. & Hannigan, Laurie John [Show all 9 contributors for this article] (2021). Genetic and environmental contributions to co-occurring ADHD and emotional problems in school-aged children. Developmental Psychology. ISSN 0012-1649. 57(8), p. 1359–1371. doi: 10.1037/dev0001229. Full text in Research Archive
• Gustavson, Kristin; Ystrøm, Eivind; Ask, Helga; Torvik, Fartein Ask; Hornig, Mady & Susser, Ezra [Show all 16 contributors for this article] (2021). Acetaminophen use during pregnancy and offspring attention deficit hyperactivity disorder - a longitudinal sibling control study. JCPP Advances. 1(2). doi: 10.1002/jcv2.12020. Full text in Research Archive Show summary

  Background: Maternal acetaminophen use during pregnancy is associated with increased risk of ADHD in the child. This could reflect causal influence of acetaminophen on fetal neurodevelopment or could be due to confounding factors. The aim of the current study was to examine unmeasured familial confounding factors of this association. Methods: We used data from 26,613 children from 12,902 families participating in the prospective Norwegian Mother, Father, and Child Cohort Study (MoBa). The MoBa was linked to the Norwegian Medical Birth Register and the Norwegian Patient Registry. Siblings discordant for prenatal acetaminophen exposure were compared regarding risk of having an ADHD diagnosis. Results: Children exposed to acetaminophen up to 28 days during pregnancy did not have increased risk of receiving an ADHD diagnosis compared to unexposed children. The adjusted Hazard ratio (aHR) was 0.87 (95% C.I. = 0.70-1.08) for exposure 1 to 7 days, and 1.13 (95% C.I. = 0.82–1.49) for 8–28 days. Long-term exposure (29 days or more) was associated with a two-fold increase in risk of ADHD diagnosis (aHR = 2.02, 95% C.I = 1.17–3.25). In the sibling control model, the association between long-term acetaminophen use and ADHD in the child was aHR = 2.77 (95% C.I. = 1.48–5.05) at the between-family level, and aHR = 1.06 (95% C.I. = 0.51–2.05) at the within-family level. Conclusions: Both the exposed and the unexposed children of mothers with long-term use of acetaminophen in one of the pregnancies had increased risk of receiving an ADHD diagnosis. This indicates that the observed association between long-term acetaminophen use during pregnancy and ADHD in the child may at least partly be confounded by unobserved family factors.

• Haan, Elis; Sallis, Hannah M.; Zuccolo, Luisa; Labrecque, Jeremy; Ystrøm, Eivind & Reichborn-Kjennerud, Ted [Show all 9 contributors for this article] (2021). Prenatal smoking, alcohol and caffeine exposure and maternal-reported attention deficit hyperactivity disorder symptoms in childhood: triangulation of evidence using negative control and polygenic risk score analyses. Addiction. ISSN 0965-2140. 117(5), p. 1458–1471. doi: 10.1111/add.15746. Full text in Research Archive Show summary

  Background and aims Studies have indicated that maternal prenatal substance use may be associated with offspring attention deficit hyperactivity disorder (ADHD) via intrauterine effects. We measured associations between prenatal smoking, alcohol and caffeine consumption with childhood ADHD symptoms accounting for shared familial factors. Design First, we used a negative control design comparing maternal and paternal substance use. Three models were used for negative control analyses: unadjusted (without confounders), adjusted (including confounders) and mutually adjusted (including confounders and partner's substance use). The results were meta-analysed across the cohorts. Secondly, we used polygenic risk scores (PRS) as proxies for exposures. Maternal PRS for smoking, alcohol and coffee consumption were regressed against ADHD symptoms. We triangulated the results across the two approaches to infer causality. Setting We used data from three longitudinal pregnancy cohorts: Avon Longitudinal Study of Parents and Children (ALSPAC) in the United Kingdom, Generation R study (GenR) in the Netherlands and Norwegian Mother, Father and Child Cohort study (MoBa) in Norway. Participants Phenotype data available for children were: NALSPAC = 5455–7751; NGENR = 1537–3119; NMOBA = 28 053–42 206. Genotype data available for mothers was: NALSPAC = 7074; NMOBA = 14 583. Measurements A measure of offspring ADHD symptoms at age 7–8 years was derived by dichotomizing scores from questionnaires and parental self-reported prenatal substance use was measured at the second pregnancy trimester. Findings The pooled estimate for maternal prenatal substance use showed an association with total ADHD symptoms [odds ratio (OR)SMOKING = 1.11, 95% confidence interval (CI) = 1.00–1.23; ORALCOHOL = 1.27, 95% CI = 1.08–1.49; ORCAFFEINE = 1.05, 95% CI = 1.00–1.11], while not for fathers (ORSMOKING = 1.03, 95% CI = 0.95–1.13; ORALCOHOL = 0.83, 95% CI = 0.47–1.48; ORCAFFEINE = 1.02, 95% CI = 0.97–1.07). However, maternal associations did not persist in sensitivity analyses (substance use before pregnancy, adjustment for maternal ADHD symptoms in MoBa). The PRS analyses were inconclusive for an association in ALSPAC or MoBa. Conclusions There appears to be no causal intrauterine effect of maternal prenatal substance use on offspring attention deficit hyperactivity disorder symptoms.

• Burdzovic, Jasmina; Torvik, Fartein Ask; Ystrøm, Eivind; Skurtveit, Svetlana; Handal, Marte & Martinez, Priscilla [Show all 8 contributors for this article] (2021). Parental Risk Constellations and Future Alcohol Use Disorder (AUD) in Offspring: A Combined HUNT Survey and Health Registries Study. Psychology of Addictive Behaviors. ISSN 0893-164X. 36(4), p. 375–386. doi: 10.1037/adb0000681. Full text in Research Archive Show summary

  Abstract Objective: We examined the risk of developing a future alcohol use disorder (AUD) among offspring of families with different constellations of parental risk factors. Method: We analyzed a sample of 8,774 offspring (50.2% male) from 6,696 two-parent families who participated in the Nord-Trøndelag Health Study in Norway when offspring were 13–19 years old in 1995–1997 or 2006–2008. Based on population registry information and parental Nord-Trøndelag Health Study self-reports, families were classified via Latent Profile Analysis into fiver risk constellations reflecting parents’ education, drinking quantities and frequencies, and mental health. Information about AUD-related diagnoses, treatments, and prescriptions for all offspring in the period between 2008 and 2016 was obtained from 3 national health registries and pooled to reflect any AUD. The likelihood of AUD in offspring was examined with a set of nested logistic regression models. Results: Registry records yielded 186 AUD cases (2.1%). Compared with the lowest-risk constellation, offspring from two constellations were more likely to present with AUD in unadjusted analyses. After adjusting for all covariates, including offspring’s alcohol consumption and witnessing parental intoxication during adolescence, AUD risk remained elevated and statistically significant (adjusted odds ratio = 2.34, 95% confidence interval = 1.14, 4.85) for offspring from the constellation characterized by at least weekly binge drinking, low education, and poor mental health in both parents. Conclusion: Weekly binge drinking by both parents was associated with future AUD risk among community offspring in Norway when clustered with additional parental risks such as poor mental health and low educational attainment.

• Haan, E; Sallis, H; Ystrøm, Eivind; Njølstad, Pål Rasmus; Andreassen, Ole & Reichborn-Kjennerud, Ted [Show all 9 contributors for this article] (2021). Maternal and offspring genetic risk score analyses of fetal alcohol exposure and attention-deficit hyperactivity disorder risk in offspring. Alcoholism: Clinical and Experimental Research. ISSN 0145-6008. 45(10), p. 2090–2102. doi: 10.1111/acer.14692. Full text in Research Archive Show summary

  Background: Studies investigating the effects of prenatal alcohol exposure on childhood attention-deficit hyperactivity disorder (ADHD) symptoms using conventional observational designs have reported inconsistent findings, which may be affected by unmeasured confounding and maternal and fetal ability to metabolize alcohol. We used genetic variants from the alcohol metabolizing genes, alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH), as proxies for fetal alcohol exposure to investigate their association with risk of offspring ADHD symptoms around age 7–8 years. Methods: We used data from 3 longitudinal pregnancy cohorts: Avon Longitudinal Study of Parents and Children (ALSPAC), Generation R study (GenR), and the Norwegian Mother, Father and Child Cohort study (MoBa). Genetic risk scores (GRS) for alcohol use and metabolism using 36 single nucleotide polymorphisms (SNPs) from ADH and ALDH genes were calculated for mothers (NALSPAC = 8196; NMOBA = 13,614), fathers (NMOBA = 13,935), and offspring (NALSPAC=8,237; NMOBA=14,112; NGENR=2,661). Associations between maternal GRS and offspring risk of ADHD symptoms were tested in the full sample to avoid collider bias. Offspring GRS analyses were stratified by maternal drinking status. Results: The pooled estimate in maternal GRS analyses adjusted for offspring GRS in ALSPAC and MoBa was OR = 0.99, 95%CI 0.97–1.02. The pooled estimate in offspring GRS analyses stratified by maternal drinking status across all the cohorts was as follows: ORDRINKING = 0.98, 95% CI 0.94–1.02; ORNO DRINKING = 0.99, 95% CI 0.97–1.02. These findings remained similar after accounting for maternal genotype data in ALSPAC and maternal and paternal genotype data in MoBa. Conclusions: We did not find evidence for a causal effect of fetal alcohol exposure on risk of ADHD symptoms in offspring. The results may be affected by limited power to detect small effects and outcome assessment.

• Degerud, Eirik Magnus Meek; Høiseth, Gudrun; Mørland, Jørg; Ariansen, Inger Kristine Holtermann; Graff-Iversen, Sidsel & Ystrøm, Eivind [Show all 9 contributors for this article] (2021). Associations of Binge Drinking with the Risks of Ischemic Heart Disease and Stroke: A Study of Pooled Norwegian Health Surveys. American Journal of Epidemiology. ISSN 0002-9262. 190(8), p. 1592–1603. doi: 10.1093/aje/kwab063. Full text in Research Archive Show summary

  Norwegian health survey data (1987 – 2003) were analysed to determine if binge drinking increases the risk of incident major events from ischemic heart disease (IHD) and stroke. Among current drinkers reporting average alcohol intakes between 2 to 60 g/day (n = 44,476), frequent binge drinking (5+ units ≥ once per month) was not associated with a greater risk of IHD (adjusted hazard ratio = 0.91, 95% confidence interval: 0.76, 1.09) nor stroke (adjusted hazard ratio = 0.98, 95% confidence interval: 0.81, 1.19), in comparison with participants who reported that they never or only infrequently (<once per month) had episodes of binge drinking. Participants with an average alcohol intake between 2 – 60 g/day had a lower risk of IHD in comparison with participants with very low intakes (<2 g/day) both among frequent binge drinkers (adjusted hazard ratio = 0.67, 95% confidence interval: 0.56, 0.80) and among never/infrequent binge drinkers (adjusted hazard ratio = 0.75, 95% confidence interval: 0.67, 0.84). The findings suggest that frequent binge drinking does not, independently of the average alcohol intake, increase the risk of incident IHD or stroke events. However, the findings should be interpreted in light of the limitations of the study design.

• Eilertsen, Espen Moen; Jami, Eshim Shahid; McAdams, Tom A.; Hannigan, Laurie J.; Havdahl, Alexandra & Magnus, Per [Show all 8 contributors for this article] (2021). Direct and Indirect Effects of Maternal, Paternal, and Offspring Genotypes: Trio-GCTA. Behavior Genetics. ISSN 0001-8244. 51, p. 154–161. doi: 10.1007/s10519-020-10036-6. Full text in Research Archive Show summary

  Indirect genetic effects from relatives may result in misleading quantifications of heritability, but can also be of interest in their own right. In this paper we propose Trio-GCTA, a model for separating direct and indirect genetic effects when genome-wide single nucleotide polymorphism data have been collected from parent-offspring trios. The model is applicable to phenotypes obtained from any of the family members. We discuss appropriate parameter interpretations and apply the method to three exemplar phenotypes: offspring birth weight, maternal relationship satisfaction, and paternal body-mass index, using real data from the Norwegian Mother, Father and Child Cohort Study (MoBa).

• Rajula, Hema Sekhar Reddy; Manchia, Mirko; Agarwal, Kratika; Akingbuwa, Wonuola A.; Allegrini, Andrea G. & Diemer, Elizabeth [Show all 31 contributors for this article] (2021). Overview of CAPICE-Childhood and Adolescence Psychopathology: unravelling the complex etiology by a large Interdisciplinary Collaboration in Europe-an EU Marie Skłodowska-Curie International Training Network. European Child and Adolescent Psychiatry. ISSN 1018-8827. p. 1–11. doi: 10.1007/s00787-020-01713-2. Full text in Research Archive Show summary

  Abstract The Roadmap for Mental Health and Wellbeing Research in Europe (ROAMER) identified child and adolescent mental illness as a priority area for research. CAPICE (Childhood and Adolescence Psychopathology: unravelling the complex etiology by a large Interdisciplinary Collaboration in Europe) is a European Union (EU) funded training network aimed at investigating the causes of individual differences in common childhood and adolescent psychopathology, especially depression, anxiety, and attention deficit hyperactivity disorder. CAPICE brings together eight birth and childhood cohorts as well as other cohorts from the EArly Genetics and Life course Epidemiology (EAGLE) consortium, including twin cohorts, with unique longitudinal data on environmental exposures and mental health problems, and genetic data on participants. Here we describe the objectives, summarize the methodological approaches and initial results, and present the dissemination strategy of the CAPICE network. Besides identifying genetic and epigenetic variants associated with these phenotypes, analyses have been performed to shed light on the role of genetic factors and the interplay with the environment in influencing the persistence of symptoms across the lifespan. Data harmonization and building an advanced data catalogue are also part of the work plan. Findings will be disseminated to non-academic parties, in close collaboration with the Global Alliance of Mental Illness Advocacy Networks-Europe (GAMIAN-Europe).

• Grzeskowiak, Luke E.; Saha, Moni R.; Ingman, Wendy V.; Nordeng, Hedvig Marie Egeland; Ystrøm, Eivind & Amir, Lisa H. (2021). Incidence, antibiotic treatment and outcomes of lactational mastitis: Findings from The Norwegian Mother, Father and Child Cohort Study (MoBa). Paediatric and Perinatal Epidemiology. ISSN 0269-5022. 36(2), p. 254–263. doi: 10.1111/ppe.12824. Full text in Research Archive
• Ask, Helga; Eilertsen, Espen Moen; Gjerde, Line Cecilie; Hannigan, Laurie John; Gustavson, Kristin & Havdahl, Alexandra [Show all 12 contributors for this article] (2021). Intergenerational transmission of parental neuroticism to emotional problems in 8-year-old children: Genetic and environmental influences. JCPP Advances. 1(4). doi: 10.1002/jcv2.12054. Full text in Research Archive Show summary

  Background Children of parents with high levels of neuroticism tend to have high neuroticism themselves as well as increased risk of experiencing symptoms of anxiety and depression. It is not yet clear how much of this link is attributable to a potential effect of parent on child (e.g., via a socializing effect) versus to shared genetic risk. We aimed to determine whether there is an intergenerational association after accounting for genetic transmission and assortative mating. Methods We used data from the Norwegian Mother, Father and Child Cohort Study including 11,088 sibling pairs in the parental generation, their partners (N = 22,176) and their offspring (N = 26,091). Exposures were maternal and paternal neuroticism (self-reported), and the outcomes were neuroticism, symptoms of depression, and symptoms of anxiety in 8-year-old children (mother-reported). Results After accounting for assortative mating in parents (phenotypic r = 0.26) and genetic transmission (explaining 0%–18% of the mother-offspring correlations), potential maternal effects explained 80% (95% CI = 47–95) of the association with offspring neuroticism (mother-child r = 0.31), 78% (95% CI = 66–89) of the association with offspring depressive symptoms (r = 0.31), and 98% (95% CI = 45–112) of the association with offspring anxiety symptoms (r = 0.16). Intergenerational transmission of genetic variants associated with paternal neuroticism accounted for ∼40% (CI = 22%–58%) of the father-offspring correlations with neuroticism and symptoms of depression (r = 0.13 and 0.13, respectively) but none with offspring symptoms of anxiety (r = 0.05). The remaining father-offspring correlations were explained by maternal influences through assortative mating. Conclusions These results are consistent with direct effects between maternal and offspring neuroticism and between maternal neuroticism and offspring symptoms of anxiety and depression. Further understanding of these intergenerational processes will require an adequate model of how these constructs (neuroticism, anxiety and depression) relate to each other within generations.

• Stoltenberg, Emil Aas; Nordeng, Hedvig Marie Egeland; Ystrøm, Eivind & Samuelsen, Sven Ove (2020). The cure model in perinatal epidemiology. Statistical Methods in Medical Research. ISSN 0962-2802. 29(10), p. 2783–2794. doi: 10.1177/0962280220904092. Full text in Research Archive Show summary

  In the statistical literature, the class of survival analysis models known as cure models has received much attention in recent years. Cure models seem not, however, to be part of the statistical toolbox of perinatal epidemiologists. In this paper, we demonstrate that in perinatal epidemiological studies where one investigates the relation between a gestational exposure and a condition that can only be ascertained after several years, cure models may provide the correct statistical framework. The reason for this is that the hypotheses being tested often concern an unobservable outcome that, in view of the hypothesis, should be thought of as occurring at birth, even though it is only detectable much later in life. The outcome of interest can therefore be viewed as a censored binary variable. We illustrate our argument with a simple cure model analysis of the possible relation between gestational exposure to paracetamol and attention-deficit hyperactivity disorder, using data from the Norwegian Mother, Father and Child Cohort Study conducted by the Norwegian Institute of Public Health, and information about the attention-deficit hyperactivity disorder diagnoses obtained from the Norwegian Patient Registry.

• Villanger, Gro Dehli; Ystrøm, Eivind; Engel, Stephanie M.; Longnecker, Matthew P.; Pettersen, Rolf Dagfinn & Rowe, Alexander D. [Show all 8 contributors for this article] (2020). Neonatal thyroid‐stimulating hormone and association with attention‐deficit/hyperactivity disorder. Paediatric and Perinatal Epidemiology. ISSN 0269-5022. 34(5), p. 590–596. doi: 10.1111/ppe.12643. Full text in Research Archive
• Torvik, Fartein Ask; Eilertsen, Espen Moen; McAdams, Tom A.; Gustavson, Kristin; Zachrisson, Henrik Daae & Brandlistuen, Ragnhild Eek [Show all 11 contributors for this article] (2020). Mechanisms linking parental educational attainment with child ADHD, depression, and academic problems: a study of extended families in The Norwegian Mother, Father and Child Cohort Study. Journal of Child Psychology and Psychiatry. ISSN 0021-9630. 61(9), p. 1009–1018. doi: 10.1111/jcpp.13197. Full text in Research Archive Show summary

  Background: Low educational attainment in parents is associated with child psychopathology. It is not clear whether the associations are due to risk factors that family members share or due to effects of maternal or paternal education on the offspring. We investigate whether associations between maternal and paternal educational attainment and child symptoms of attention deficit/hyperactivity disorder (ADHD), depression, and academic problems are due to shared genetic factors, shared family environmental factors, or effects of the parental phenotype educational attainment itself. Methods: This study is based on the Norwegian Mother, Father and Child Cohort Study (MoBa). The sample comprised 34,958 children (17,128 girls) in 28,372 extended‐family units. We used data from related nuclear families linked by siblings in the parent generation. We applied a quasi‐experimental extended children‐of‐twins design that included siblings in both generations and took account of nonrandom mating by including partners. Educational attainment was self‐reported by mothers and fathers. Mothers reported children's symptoms of ADHD, symptoms of depression, and academic problems by questionnaire when the children were 8 years old. Results: Children of lowly educated parents scored higher on all outcomes and had an approximate doubling of the risk of high symptom levels. The association between maternal and paternal educational attainment and child symptoms of ADHD and academic problems persisted after controlling for shared genetic and family environmental factors. Phenotypic transmission to depression was weaker and in the best fitting model fully explained by genetic factors shared by the two generations. Conclusions: Associations between educational attainment of mothers and fathers and child symptoms of ADHD and academic problems could not be ascribed to shared familial risk factors, whereas associations with symptoms of depression could. Parental education or resources and behaviors resulting from low education might be targets of interventions aimed at reducing symptoms of ADHD and academic problems.

• Kjeldsen, Anne; Nes, Ragnhild Bang; Sanson, Ann; Ystrøm, Eivind & Karevold, Evalill Bølstad (2020). Understanding trajectories of externalizing problems: Stability and emergence of risk factors from infancy to middle adolescence. Development and Psychopathology. ISSN 0954-5794. 33(1), p. 264–283. doi: 10.1017/S0954579419001755. Full text in Research Archive
• Lund, Ingunn Olea; Eilertsen, Espen Moen; Gjerde, Line C.; Torvik, Fartein Ask; Røysamb, Espen & Reichborn-Kjennerud, Ted [Show all 7 contributors for this article] (2020). Maternal Drinking and Child Emotional and Behavior Problems. Pediatrics. ISSN 0031-4005. 145(3). doi: 10.1542/peds.2019-2007. Full text in Research Archive
• Cheesman, Rosa; Eilertsen, Espen Moen; Ahmadzadeh, Yasmin I.; Gjerde, Line C.; Hannigan, Laurie John & Havdahl, Alexandra [Show all 13 contributors for this article] (2020). How important are parents in the development of child anxiety and depression? A genomic analysis of parent-offspring trios in the Norwegian Mother Father and Child Cohort Study (MoBa). BMC Medicine. 18. doi: 10.1186/s12916-020-01760-1. Full text in Research Archive Show summary

  Background Many studies detect associations between parent behaviour and child symptoms of anxiety and depression. Despite knowledge that anxiety and depression are influenced by a complex interplay of genetic and environmental risk factors, most studies do not account for shared familial genetic risk. Quantitative genetic designs provide a means of controlling for shared genetics, but rely on observed putative exposure variables, and require data from highly specific family structures. Methods The intergenerational genomic method, Relatedness Disequilibrium Regression (RDR), indexes environmental effects of parents on child traits using measured genotypes. RDR estimates how much the parent genome influences the child indirectly via the environment, over and above effects of genetic factors acting directly in the child. This ‘genetic nurture’ effect is agnostic to parent phenotype and captures unmeasured heritable parent behaviours. We applied RDR in a sample of 11,598 parent-offspring trios from the Norwegian Mother, Father and Child Cohort Study (MoBa) to estimate parental genetic nurture separately from direct child genetic effects on anxiety and depression symptoms at age 8. We tested for mediation of genetic nurture via maternal anxiety and depression symptoms. Results were compared to a complementary non-genomic pedigree model. Results Parental genetic nurture explained 14% of the variance in depression symptoms at age 8. Subsequent analyses suggested that maternal anxiety and depression partially mediated this effect. The genetic nurture effect was mirrored by the finding of family environmental influence in our pedigree model. In contrast, variance in anxiety symptoms was not significantly influenced by common genetic variation in children or parents, despite a moderate pedigree heritability. Conclusions Genomic methods like RDR represent new opportunities for genetically sensitive family research on complex human traits, which until now has been largely confined to adoption, twin and other pedigree designs. Our results are relevant to debates about the role of parents in the development of anxiety and depression in children, and possibly where to intervene to reduce problems.

• Øie, Merete Glenne; Aarnes, Ingebjørg Emilie; Eilertsen, Lise Horndalsveen; Söderström, Kerstin; Ystrøm, Eivind & Håkansson, UIrika (2020). High levels of the openness trait are associated with better parental reflective functioning in mothers with substance use disorders. Addictive Behaviors Reports. ISSN 2352-8532. 12. doi: 10.1016/j.abrep.2020.100318. Full text in Research Archive Show summary

  Aims: Mothers with substance use disorders (SUD) often show impairments in parental reflective functioning (PRF), which may have adverse effects on their capacity for sensitive caregiving. Parenting personality is also associated with caregiving. However, no studies have investigated how these individual factors may contribute to variance in PRF in mothers with SUD. In this study PRF and personality were assessed in 43 mothers with SUD. Methods: PRF was assessed by the Parent Development Interview. Personality traits were assessed by the Revised Neuroticism-Extraversion-Openness Personality Inventory. Results: The results indicate that higher levels of the Openness trait are associated with better PRF. Conclusion Mothers low in Openness may need more specific and situational training in interpreting mental states in their children. Highly open mothers with SUD will likely need more help distinguishing the child’s mental states from their own, and might need help to maintain mutuality and regulating the intensity of their responses to the child’s behavior.

• Czajkowski, Nikolai Olavi; Kendler, Kenneth S; Torvik, Fartein Ask; Ystrøm, Eivind; Rosenström, Tom Henrik & Gillespie, Nathan [Show all 7 contributors for this article] (2020). Caffeine consumption, toxicity, tolerance and withdrawal; shared genetic influences with normative personality and personality disorder traits. Experimental and clinical psychopharmacology. ISSN 1064-1297. doi: 10.1037/pha0000429. Full text in Research Archive
• Sivertsen, Børge; Harvey, Allison G.; Reichborn-Kjennerud, Ted; Ystrøm, Eivind & Hysing, Mari (2020). Sleep problems and depressive symptoms in toddlers and 8-year-old children: A longitudinal study. Journal of Sleep Research. ISSN 0962-1105. 30(1), p. 1–10. doi: 10.1111/jsr.13150. Full text in Research Archive Show summary

  Sleep and depression are interlinked throughout the lifespan, but very few studies have examined the directionality of the sleep–depression link in children. The aim of the current study was to prospectively examine the bidirectional association between sleep problems and internalizing problems and depressive symptoms in toddlers and children aged 1.5 and 8 years. Data stem from the large ongoing population‐based longitudinal study, the Norwegian Mother, Father and Child Cohort Study, recruited from October 1999 to July 2009. A total of 35,075 children were included. Information on sleep duration, nocturnal awakenings and internalizing problems (Child Behaviour Checklist) was provided by the mothers at 1.5 years, whereas data on sleep duration and depressive symptoms (Short Mood and Feelings Questionnaire) were provided by the mothers when the children were 8 years old. Odds ratios (ORs) were calculated using logistic regression analyses. After accounting for previous internalizing problems, short sleep duration (≤10 hr) and frequent (≥3) nightly awakenings at 1.5 years predicted the development of depressive symptoms at 8 years of age (adjusted OR = 1.28; 95% confidence interval [CI] 1.08–1.51, and adjusted OR = 1.27, 95% CI 1.08–1.50, respectively). Also, internalizing problems at 1.5 years predicted onset of later short sleep duration (adjusted OR = 1.83, 95% CI 1.32–2.54) after accounting for early sleep problems. This prospective study demonstrated a bidirectional association between sleep and internalizing/depressive symptoms from toddlerhood to middle childhood. Intervention studies are needed to examine whether targeting either of these problems at this early age may prevent onset of the other.

• Akingbuwa, Wonuola A.; Hammerschlag, Anke R.; Jami, Eshim S.; Allegrini, Andrea G.; Karhunen, Ville & Sallis, Hannah [Show all 35 contributors for this article] (2020). Genetic Associations Between Childhood Psychopathology and Adult Depression and Associated Traits in 42 998 Individuals: A Meta-analysis. JAMA psychiatry. ISSN 2168-6238. 77(7), p. 715–728. doi: 10.1001/jamapsychiatry.2020.0527. Full text in Research Archive
• Jami, Eshim; Eilertsen, Espen Moen; Hammerschlag, Anke R.; Qiao, Zhen; Evans, David M. & Ystrøm, Eivind [Show all 8 contributors for this article] (2020). Maternal and paternal effects on offspring internalizing problems: Results from genetic and family‐based analyses. American Journal of Medical Genetics Part B: Neuropsychiatric Genetics. ISSN 1552-4841. 183(5), p. 258–267. doi: 10.1002/ajmg.b.32784. Full text in Research Archive Show summary

  It is unclear to what extent parental influences on the development of internalizing problems in offspring are explained by indirect genetic effects, reflected in the environment provided by the parent, in addition to the genes transmitted from parent to child. In this study, these effects were investigated using two innovative methods in a large birth cohort. Using maternal‐effects genome complex trait analysis (M‐GCTA), the effects of offspring genotype, maternal or paternal genotypes, and their covariance on offspring internalizing problems were estimated in 3,801 mother–father–child genotyped trios. Next, estimated genetic correlations within pedigree data, including 10,688 children, were used to estimate additive genetic effects, maternal and paternal genetic effects, and a shared family effect using linear mixed effects modeling. There were no significant maternal or paternal genetic effects on offspring anxiety or depressive symptoms at age 8, beyond the effects transmitted via the genetic pathway between parents and children. However, indirect maternal genetic effects explained a small, but nonsignificant, proportion of variance in childhood depressive symptoms in both the M‐GCTA (~4%) and pedigree (~8%) analyses. Our results suggest that parental effects on offspring internalizing problems are predominantly due to transmitted genetic variants, rather than the indirect effect of parental genes via the environment.

• Eilertsen, Espen Moen; Hannigan, Laurie John; McAdams, Tom A.; Rijsdijk, Frühling V.; Czajkowski, Nikolai Olavi & Reichborn-Kjennerud, Ted [Show all 8 contributors for this article] (2020). Parental Prenatal Symptoms of Depression and Offspring Symptoms of ADHD: A Genetically Informed Intergenerational Study. Journal of Attention Disorders. ISSN 1087-0547. April 26(April). doi: 10.1177/1087054720914386. Full text in Research Archive
• Degerud, Eirik Magnus Meek; Høiseth, Gudrun; Mørland, Jørg Gustav; Ariansen, Inger; Graff-Iversen, Sidsel & Ystrøm, Eivind [Show all 8 contributors for this article] (2020). Association of coincident self-reported mental health problems and alcohol intake with all-cause and cardiovascular disease mortality: A Norwegian pooled population analysis. PLoS Medicine. ISSN 1549-1277. 17(2), p. 1–21. doi: 10.1371/journal.pmed.1003030. Full text in Research Archive Show summary

  Background The disease burden attributable to mental health problems and to excess or harmful alcohol use is considerable. Despite a strong relationship between these 2 important factors in population health, there are few studies quantifying the mortality risk associated with their co-occurrence in the general population. The aim of this study was therefore to investigate cardiovascular disease (CVD) and all-cause mortality according to self-reported mental health problems and alcohol intake in the general population. Methods and findings We followed 243,372 participants in Norwegian health surveys (1994–2002) through 2014 for all-cause and CVD mortality by data linkage to national registries. The mean (SD) age at the time of participation in the survey was 43.9 (10.6) years, and 47.8% were men. During a mean (SD) follow-up period of 16.7 (3.2) years, 6,587 participants died from CVD, and 21,376 died from all causes. Cox models estimated hazard ratios (HRs) with 95% CIs according to a mental health index (low, 1.00–1.50; high, 2.01–4.00; low score is favourable) based on the General Health Questionnaire and the Hopkins Symptom Checklist, and according to self-reported alcohol intake (low, <2; light, 2–11.99; moderate, 12–23.99; high, ≥24 grams/day). HRs were adjusted for age, sex, educational level, marital status, and CVD risk factors. Compared to a reference group with low mental health index score and low alcohol intake, HRs (95% CIs) for all-cause mortality were 0.93 (0.89, 0.97; p = 0.001), 1.00 (0.92, 1.09; p = 0.926), and 1.14 (0.96, 1.35; p = 0.119) for low index score combined with light, moderate, and high alcohol intake, respectively. HRs (95% CIs) were 1.22 (1.14, 1.31; p < 0.001), 1.24 (1.15, 1.33; p < 0.001), 1.43 (1.23, 1.66; p < 0.001), and 2.29 (1.87, 2.80; p < 0.001) for high index score combined with low, light, moderate, and high alcohol intake, respectively. For CVD mortality, HRs (95% CIs) were 0.93 (0.86, 1.00; p = 0.058), 0.90 (0.76, 1.07; p = 0.225), and 0.95 (0.67, 1.33; p = 0.760) for a low index score combined with light, moderate, and high alcohol intake, respectively, and 1.11 (0.98, 1.25; p = 0.102), 0.97 (0.83, 1.13; p = 0.689), 1.01 (0.71, 1.44; p = 0.956), and 1.78 (1.14, 2.78; p = 0.011) for high index score combined with low, light, moderate, and high alcohol intake, respectively. HRs for the combination of a high index score and high alcohol intake (HRs: 2.29 for all-cause and 1.78 for CVD mortality) were 64% (95% CI 53%, 74%; p < 0.001) and 69% (95% CI 42%, 97%; p < 0.001) higher than expected for all-cause mortality and CVD mortality, respectively, under the assumption of a multiplicative interaction structure. A limitation of our study is that the findings were based on average reported intake of alcohol without accounting for the drinking pattern. Conclusions In the general population, the mortality rates associated with more mental health problems and a high alcohol intake were increased when the risk factors occurred together.

• Rosenström, Tom Henrik; Torvik, Fartein Ask; Ystrøm, Eivind; Aggen, Steven H.; Gillespie, Nathan A. & Krueger, Robert F. [Show all 9 contributors for this article] (2020). Specific Antisocial and Borderline Personality Disorder Criteria and General Substance Use: A Twin Study. Personality Disorders: Theory, Research, and Treatment. ISSN 1949-2715. 12(3), p. 228–240. doi: 10.1037/per0000404. Full text in Research Archive
• Heiberg, Ina Heidi; Nesvåg, Ragnar; Balteskard, Lise; Bramness, Jørgen Gustav; Hultman, Christina M. & Næss, Øyvind [Show all 10 contributors for this article] (2020). Diagnostic tests and treatment procedures performed prior to cardiovascular death in individuals with severe mental illness. Acta Psychiatrica Scandinavica. ISSN 0001-690X. 141(5), p. 439–451. doi: 10.1111/acps.13157. Full text in Research Archive Show summary

  <p><i>Objective - </i>To examine whether severe mental illnesses (i.e., schizophrenia or bipolar disorder) affected diagnostic testing and treatment for cardiovascular diseases in primary and specialized health care. <p><i>Methods - </i>We performed a nationwide study of 72 385 individuals who died from cardiovascular disease, of whom 1487 had been diagnosed with severe mental illnesses. Log‐binomial regression analysis was applied to study the impact of severe mental illnesses on the uptake of diagnostic tests (e.g., 24‐h blood pressure, glucose/HbA1c measurements, electrocardiography, echocardiography, coronary angiography, and ultrasound of peripheral vessels) and invasive cardiovascular treatments (i.e., revascularization, arrhythmia treatment, and vascular surgery). <p><i>Results - </i>Patients with and without severe mental illnesses had similar prevalences of cardiovascular diagnostic tests performed in primary care, but patients with schizophrenia had lower prevalences of specialized cardiovascular examinations (prevalence ratio (PR) 0.78; 95% CI 0.73–0.85). Subjects with severe mental illnesses had lower prevalences of invasive cardiovascular treatments (schizophrenia, PR 0.58; 95% CI 0.49–0.70, bipolar disorder, PR 0.78; 95% CI 0.66–0.92). The prevalence of invasive cardiovascular treatments was similar in patients with and without severe mental illnesses when cardiovascular disease was diagnosed before death. <p><i>Conclusion - </i>Better access to specialized cardiovascular examinations is important to ensure equal cardiovascular treatments among individuals with severe mental illnesses.

• Zambrana, Imac Maria; Vollrath, Margarete Erika Maria Torgerse; Jacobsson, Bo; Sengpiel, Verena & Ystrøm, Eivind (2020). Preterm birth and risk for language delays before school entry: A sibling-control study. Development and Psychopathology. ISSN 0954-5794. doi: 10.1017/S0954579419001536. Full text in Research Archive Show summary

  We investigated whether children born preterm are at risk for language delay using a sibling-control design in the Norwegian Mother and Child Cohort Study (MoBa), conducted by the Norwegian Institute of Public Health. Participants included 26,769 siblings born between gestational weeks 23 and 42. Language delay was assessed when the children were 1.5, 3, and 5 years old. To adjust for familial risk factors, comparisons were conducted between preterm and full-term siblings. Pregnancy-specific risk factors were controlled for by means of observed variables. Findings showed that preterm children born before week 37 had increased risk for language delays at 1.5 years. At 3 and 5 years, only children born before week 34 had increased risk for language delay. Children born weeks 29–33 and before week 29 had increased risk for language delay at 1.5 years (RR = 4.51, 95% CI [3.45, 5.88]; RR = 10.32, 95% CI [6.7, 15.80]), 3 years (RR = 1.50, 95% CI [1.02, 2.21]; RR = 2.78, 95% CI [1.09, 7.07]), and 5 years (RR = 1.63, 95% CI [1.06, 2.51]; RR = 2.98, 95% CI [0.87, 10.26]), respectively. In conclusion, children born preterm are at risk for language delays, with familial confounders only explaining a moderate share of the association. This suggests a cause-effect relationship between early preterm birth and risk for language delay in preschool children.

• Hjorth, Sarah; Bromley, Rebecca; Ystrom, Eivind; Lupattelli, Angela; Spigset, Olav & Nordeng, Hedvig Marie Egeland (2019). Use and validity of child neurodevelopment outcome measures in studies on prenatal exposure to psychotropic and analgesic medications – A systematic review. PLOS ONE. 14(7), p. 1–37. doi: 10.1371/journal.pone.0219778. Full text in Research Archive Show summary

  In recent years there has been increased attention to child neurodevelopment in studies on medication safety in pregnancy. Neurodevelopment is a multifactorial outcome that can be assessed by various assessors, using different measures. This has given rise to a debate on the validity of various measures of neurodevelopment. The aim of this review was twofold. Firstly we aimed to give an overview of studies on child neurodevelopment after prenatal exposure to central nervous system acting medications using psychotropics and analgesics as examples, giving special focus on the use and validity of outcome measures. Secondly, we aimed to give guidance on how to conduct and interpret medication safety studies with neurodevelopment outcomes. We conducted a systematic review in the MEDLINE, Embase, PsycINFO, Web of Science, Scopus, and Cochrane databases from inception to April 2019, including controlled studies on prenatal exposure to psychotropics or analgesics and child neurodevelopment, measured with standardised psychometric instruments or by diagnosis of neurodevelopmental disorder. The review management tool Covidence was used for data-extraction. Outcomes were grouped as motor skills, cognition, behaviour, emotionality, or “other”. We identified 110 eligible papers (psychotropics, 82 papers, analgesics, 29 papers). A variety of neurodevelopmental outcome measures were used, including 27 different psychometric instruments administered by health care professionals, 15 different instruments completed by parents, and 13 different diagnostic categories. In 23 papers, no comments were made on the validity of the outcome measure. In conclusion, establishing neurodevelopmental safety includes assessing a wide variety of outcomes important for the child’s daily functioning including motor skills, cognition, behaviour, and emotionality, with valid and reliable measures from infancy through to adolescence. Consensus is needed in the scientific community on how neurodevelopment should be assessed in medication safety in pregnancy studies.

• Cohen, Jacqueline Mallory; Wood, Mollie; Hernandez-Diaz, Sonia; Ystrøm, Eivind & Nordeng, Hedvig Marie Egeland (2019). Paternal antidepressant use as a negative control for maternal use: assessing familial confounding on gestational length and anxiety traits in offspring. International Journal of Epidemiology. ISSN 0300-5771. 48(5), p. 1665–1672. doi: 10.1093/ije/dyz170. Full text in Research Archive Show summary

  Background Maternal antidepressant use in pregnancy has been associated with both shorter gestational length and child anxiety. We employed paternal antidepressant use as a negative-control exposure to indirectly assess whether confounding by genetic or shared familial environmental factors associated with depression may explain these associations. Methods The study sample came from the population-based Norwegian Mother and Child Cohort Study (MoBa) that recruited participants from 1999 to 2008. We included 70 959 families where the father completed a questionnaire about medication use in the 6 months prior to pregnancy. In 42 511 infants who completed the 3-year follow-up, we computed Z-scores for the anxiety domain of the Child Behavior Checklist. We used linear and logistic regression to assess the association between paternal antidepressant use, gestational age at birth and child anxiety. Results Antidepressants were used by 1.1% (n = 755) of fathers. Paternal antidepressant use was not associated with gestational age at birth [β = 0.63 days, 95% confidence interval (CI) –1.56, 0.31] whereas it was positively associated with a child anxiety symptom Z-score and high anxiety symptoms (odds ratio 1.33, 95% CI 0.90, 1.97) in unadjusted analyses. This association was attenuated when controlling for maternal and paternal history of depression and other measured factors (odds ratio 1.14, 95% CI 0.76, 1.69). Conclusions These results support the suggested effect of maternal use of antidepressants in pregnancy on shorter gestation; however, they suggest familial confounding could explain the association between maternal use of antidepressants and anxiety traits in the offspring.

• Hartman, Sarah; Eilertsen, Espen Moen; Ystrøm, Eivind; Belsky, Jay & Gjerde, Line C. (2019). Does prenatal stress amplify effects of postnatal maternal depressive and anxiety symptoms on child problem behavior? Developmental Psychology. ISSN 0012-1649. 56(1), p. 128–137. doi: 10.1037/dev0000850. Full text in Research Archive Show summary

  Emerging evidence suggests that prenatal stress does not solely undermine child functioning but increases developmental plasticity to both negative and positive postnatal experiences. Here we test this proposition using the Norwegian Mother and Child Cohort study while implementing an extreme-group (i.e., high vs. low prenatal stress) design (n = 27,889 children for internalizing and n = 27,892 for externalizing problems). To measure prenatal stress, mothers reported on depressive and anxiety symptoms at gestational weeks 17 and 30 and of stressful life events at gestational week 30. We then evaluated whether, collectively, such prenatal stress amplified the effect of mothers’ postnatal depressive and anxiety symptoms on children’s internalizing and externalizing behavior problems at age 5 years. Results showed prenatal stress amplified effects of postnatal maternal depression/anxiety on child internalizing but not externalizing behavior, with some indication that this Prenatal-Stress-×-Postnatal-Maternal-Depression interaction proved more consistent with differential susceptibility than diathesis stress thinking: Children exposed to prenatal stress evinced greater internalizing problems if exposed to more postnatal maternal depressive/anxiety symptoms and, somewhat less strongly, displayed less internalizing problems if they experienced lower postnatal maternal depressive/anxiety symptoms. However, analyses using the whole sample instead of extreme groups yielded opposing results with children exposed to the least prenatal stress evincing greater sensitivity to postnatal maternal depressive/anxiety symptoms with regards to externalizing and internalizing behavior. Taken together, it appears that prenatal stress may have differing effects on plasticity depending on prenatal stress severity.

• Gjerde, Line C.; Eilertsen, Espen Moen; Hannigan, Laurie; Eley, Thalia C.; Røysamb, Espen & Reichborn-Kjennerud, Ted [Show all 9 contributors for this article] (2019). Associations between maternal depressive symptoms and risk for offspring early-life psychopathology: the role of genetic and non-genetic mechanisms. Psychological Medicine. ISSN 0033-2917. doi: 10.1017/s0033291719003301. Full text in Research Archive Show summary

  Background Although maternal depressive symptoms are robustly associated with offspring early-life psychopathology symptoms, it is not clear which potential mechanisms are at play. We aimed to estimate the relative importance of genetic transmission and direct environmental exposure in these associations on three occasions in early childhood. Methods Biometric modeling of maternal sisters and their offspring from the Norwegian Mother and Child Cohort Study. The analyzed sample comprised 22 316 mothers and 35 589 offspring. Mothers reported their own depressive symptoms using the Symptom checklist, and offspring's concurrent symptoms of psychopathology using the Child Behavior Checklist at 1.5, 3, and 5 years postpartum. Results Associations between maternal symptoms of depression and offspring emotional problems were predominantly explained by passive genetic transmission at 1.5 and 3 years postpartum. At age 5, associations were more due to direct environmental exposure. For offspring behavioral problems, there was no net increase in the importance of direct environmental exposure across occasions. Conclusions Associations between maternal depressive symptoms and offspring psychopathology symptoms remained after accounting for shared genes, consistent with a small, causal effect. For offspring emotional problems, this effect appeared to increase in importance over time. Our findings imply that treatment of maternal depressive symptoms could also benefit the offspring, and that genetic confounding should be considered in future studies of such mother–offspring associations.

• Trønnes, Johanne Naper; Wood, Mollie; Lupattelli, Angela; Ystrøm, Eivind & Nordeng, Hedvig Marie Egeland (2019). Prenatal paracetamol exposure and neurodevelopmental outcomes in preschool-aged children. Paediatric and Perinatal Epidemiology. ISSN 0269-5022. 34(3), p. 247–256. doi: 10.1111/ppe.12568. Full text in Research Archive Show summary

  Background Recent studies have suggested an association between prenatal paracetamol exposure and adverse neurodevelopmental outcomes in children. However, these findings may be confounded by unmeasured factors related to maternal use of paracetamol and child outcomes. Objective To examine the association between duration and timing of prenatal paracetamol exposure on parent‐reported communication skills, behaviour, and temperament in preschool‐aged children, with focus on the role of unmeasured confounding. Methods We used data from the Norwegian Mother and Child Cohort Study. Linear and generalised linear models with inverse probability weights and robust standard errors were used to quantify the association between prenatal paracetamol exposure and continuous and categorical outcomes. Results Of the 32 934 children included in our study, 8374 (25.4%), 4961 (15.1%), and 1791 (5.4%) were prenatally exposed to paracetamol in one, two, and three trimesters, respectively. Children exposed to paracetamol in two trimesters scored lower on shyness compared with unexposed children (β −0.62, 95% confidence interval [CI] −1.05, −0.19). Children exposed to paracetamol in three trimesters had a moderate increased risk of internalising behaviour problems (relative risk (RR) 1.36, 95% CI 1.02, 1.80) and borderline externalising behaviour problems (RR 1.22, 95% CI 0.93, 1.60) compared with unexposed children. Children exposed to paracetamol in 2nd/3rd trimester scored lower on shyness (β −0.32, 95% CI −0.66, 0.02) compared with unexposed children. Sensitivity analyses indicated that unmeasured confounders play an important role and may potentially bias the effect estimates away from the null. Conclusions Timing of exposure and short‐term use of paracetamol during pregnancy do not seem to pose any substantial risk of the outcomes examined. Although we found an association between paracetamol use in multiple trimesters and lower shyness and greater internalising behaviour in preschool‐aged children, we cannot rule out chance or unmeasured confounding as possible explanations for these findings.

• Rosenström, Tom Henrik; Czajkowski, Nikolai Olavi; Ystrøm, Eivind; Krueger, Robert F; Aggen, Steven H & Gillespie, Nathan A [Show all 9 contributors for this article] (2019). Genetically Informative Mediation Modeling Applied to Stressors and Personality-Disorder Traits in Etiology of Alcohol Use Disorder. Behavior Genetics. ISSN 0001-8244. 49(1), p. 11–23. doi: 10.1007/s10519-018-9941-z. Full text in Research Archive
• Torvik, Fartein Ask; Rosenström, Tom Henrik; Gustavson, Kristin; Ystrøm, Eivind; Kendler, Kenneth S. & Bramness, Jørgen Gustav [Show all 8 contributors for this article] (2019). Explaining the association between anxiety disorders and alcohol use disorder: A twin study. Depression and Anxiety. ISSN 1091-4269. 36(6), p. 522–532. doi: 10.1002/da.22886. Full text in Research Archive Show summary

  <p><i>Background - </i>It is unknown whether social anxiety disorder (SAD) has a unique association with alcohol use disorder (AUD) over and beyond that of other anxiety disorders, how the associations develop over time, and whether the associations are likely to be causal. <p><i>Methods - </i>Diagnoses of AUD, SAD, generalized anxiety disorder, panic disorder, agoraphobia, and specific phobias were assessed twice using the Composite International Diagnostic Interview among 2,801 adult Norwegian twins. The data were analyzed using logistic regression analyses and multivariate biometric structural equation modeling. <p><i>Results - </i>SAD had the strongest association with AUD, and SAD predicted AUD over and above the effect of other anxiety disorders. In addition, SAD was prospectively associated with AUD, whereas other anxiety disorders were not. AUD was associated with a slightly elevated risk of later anxiety disorders other than SAD. Biometric modeling favored a model where SAD influenced AUD compared to models where the relationship was reversed or due to correlated risk factors. Positive associations between AUD and other anxiety disorders were fully explained by shared genetic risk factors. <p><i>Conclusions - </i>Unlike other anxiety disorders, SAD plausibly has a direct effect on AUD. Interventions aimed at prevention or treatment of SAD may have an additional beneficial effect of preventing AUD, whereas interventions aimed at other anxiety disorders are unlikely to have a similar sequential effect on AUD.

• Lund, Ingunn Olea; Eilertsen, Espen Moen; Gjerde, Line C.; Røysamb, Espen; Wood, Mollie & Reichborn-Kjennerud, Ted [Show all 7 contributors for this article] (2019). Is the association between maternal alcohol consumption in pregnancy and pre-school child behavioural and emotional problems causal? Multiple approaches for controlling unmeasured confounding. Addiction. ISSN 0965-2140. 114(6), p. 1004–1014. doi: 10.1111/add.14573. Full text in Research Archive Show summary

  Background and aims Hazardous drinking (i.e. alcohol consumption that places drinkers at risk for adverse health outcomes) during pregnancy is associated with adverse child outcomes. To address whether the associations are causal, we aimed to estimate the effect of maternal hazardous drinking during the first trimester on offspring emotional and behavioural problems throughout the pre‐school age. We adjusted for: (1) measured confounding (e.g. smoking), (2) familial risk factors by sibling control design and (3) non‐shared environmental risk factors by using hazardous drinking the 3 months before pregnancy as an instrumental variable. Design Prospective cohort study. Participants were recruited between 1999 and 2009 at ultrasound examination offered to all pregnant women in Norway. Data were collected during the 17th and the 30th weeks of gestation, and when the children were aged 1.5, 3 and 5 years. Setting Norway, 1999–2015. Participants The sample consisted of 14 639 mothers with 25 744 offspring siblings from the Norwegian Mother and Child Cohort Study. Measurements Respondents self‐reported on: alcohol consumption, children's emotional problems (i.e. emotional reactive, anxiety/depression, somatic complaints) and children's behavioural problems (i.e. attention and aggressive behaviour) throughout pre‐school age. We used longitudinal latent growth curve models to estimate the effect of maternal drinking during the first trimester on offspring emotional and behavioural problems. Findings Most associations were strongly reduced after controlling for both familial and measured environmental risk factors. After adjustment, exposed children were more emotionally reactive [β = 2.33; 95% confidence interval (CI) = 0.13–4.53] and had more somatic complaints (β = 1.93; 95% CI = 0.09–3.77) at age 3, but not at age 5. Exposed children were less aggressive than unexposed siblings at age 5 (β = −2.27; 95% CI = –4.02 to –0.52). Conclusions Children exposed to their mothers’ hazardous drinking during the first trimester appear to be more emotionally reactive and have more somatic complaints at age 3, but not at age 5, and are less aggressive at age 5 compared with unexposed siblings.

• Gustavson, Kristin; Ask, Helga; Ystrøm, Eivind; Stoltenberg, Camilla; Lipkin, W. Ian & Suren, Pål [Show all 16 contributors for this article] (2019). Maternal fever during pregnancy and offspring attention deficit hyperactivity disorder. Scientific Reports. 9:9519, p. 1–10. doi: 10.1038/s41598-019-45920-7. Full text in Research Archive Show summary

  Maternal fever during pregnancy is associated with several adverse child outcomes. We investigated associations between maternal fever and ADHD among offspring, as well as the sub-dimensions of ADHD - inattention and hyperactivity/impulsivity. Data came from the Norwegian Mother and Child Cohort Study, including more than 114,000 children. Information about children’s ADHD diagnoses was obtained from the Norwegian Patient Register. Mothers reported on inattention and hyperactivity/impulsivity symptoms in questionnaires at 8 years. Logistic regression analysis showed that children exposed to maternal fever in the first trimester received an ADHD diagnosis more often than unexposed children (Odds Ratio (OR) = 1.31, 95% confidence interval (CI) = 1.06–1.61). For children exposed twice or more in the first trimester, the OR was 2.64 (CI = 1.36–5.14). Linear regression analysis showed elevated inattention symptoms among children exposed to fever in the first (Cohen’s d = 0.09, CI = 0.03–0.15) and second (Cohen’s d = 0.05, CI = 0.01–0.09) trimester. Results were similar whether the mother had taken acetaminophen for their fever or not. Hyperactivity/impulsivity symptoms were not related to maternal fever. The results indicate that maternal fever in early pregnancy may be a risk factor for ADHD, and particularly for inattention problems. This risk is neither mitigated nor inflated by use of acetaminophen.

• Lund, Ingunn Olea; Skurtveit, Svetlana; Handal, Marte; Bukten, Anne; Torvik, Fartein Ask & Ystrøm, Eivind [Show all 7 contributors for this article] (2019). Association of constellations of parental risk with children's subsequent anxiety and depression: Findings from a HUNT survey and health registry study. JAMA pediatrics. ISSN 2168-6203. 173(3), p. 251–259. doi: 10.1001/jamapediatrics.2018.4360. Full text in Research Archive
• Heiberg, Ina Heidi; Jacobsen, Bjarne K.; Balteskard, Lise; Bramness, Jørgen Gustav; Næss, Øyvind & Ystrøm, Eivind [Show all 10 contributors for this article] (2019). Undiagnosed cardiovascular disease prior to cardiovascular death in individuals with severe mental illness. Acta Psychiatrica Scandinavica. ISSN 0001-690X. 139(6), p. 558–571. doi: 10.1111/acps.13017. Full text in Research Archive Show summary

  <p><i>Objective - </i>To examine whether individuals with schizophrenia (SCZ) or bipolar disorder (BD) had equal likelihood of not being diagnosed with cardiovascular disease (CVD) prior to cardiovascular death, compared to individuals without SCZ or BD. <p><i>Methods - </i>Multivariate logistic regression analysis including nationwide data of 72 451 cardiovascular deaths in the years 2011–2016. Of these, 814 had a SCZ diagnosis and 673 a BD diagnosis in primary or specialist health care. <p><i>Results - </i>Individuals with SCZ were 66% more likely (OR: 1.66; 95% CI: 1.39–1.98), women with BD were 38% more likely (adjusted OR: 1.38; 95% CI: 1.04–1.82), and men with BD were equally likely (OR: 0.88, 95% CI: 0.63–1.24) not to be diagnosed with CVD prior to cardiovascular death, compared to individuals without SMI. Almost all (98%) individuals with SMI and undiagnosed CVD had visited primary or specialized somatic health care prior to death, compared to 88% among the other individuals who died of CVD. <p><i>Conclusion - </i>Individuals with SCZ and women with BD are more likely to die due to undiagnosed CVD, despite increased risk of CVD and many contacts with primary and specialized somatic care. Strengthened efforts to prevent, recognize, and treat CVD in individuals with SMI from young age are needed.

• Kendler, Kenneth S.; Aggen, Steven H.; Gillespie, Nathan; Czajkowski, Nikolai Olavi; Ystrøm, Eivind & Reichborn-Kjennerud, Ted (2019). A twin study of cigarette and snus initiation and quantity of use in Norwegian Adult Twins. Twin Research and Human Genetics. ISSN 1832-4274. 22(2), p. 108–113. doi: 10.1017/thg.2019.9. Full text in Research Archive Show summary

  While snus has been the focus of increasing public health interest, twin studies have examined neither sources of individual variation for its use nor the sources of resemblance between snus and cigarette use. Twins from the Norwegian Institute of Public Health Panel were assessed by self-report questionnaire for the initiation of regular use and maximal quantity used for snus and cigarettes. Twin modeling was performed using OpenMx on data from 2767 twins including 856 complete pairs. Fitting univariate twin models produced similar results for cigarette initiation and quantity with estimates of additive genetic, shared environmental and unique environmental effects of approximately 77%, 0% and 23%, respectively. Estimates of snus initiation and quantity were, respectively, approximately 53%, 26% and 21%. Joint analyses suggested that the genetic, shared environmental and unique environmental correlations between cigarette and snus initiation and quantity were +.82, 0 and +.42, respectively. However, these results could not be statistically distinguished from a model which postulated that resemblance between cigarette initiation and quantity resulted from genetic and unique environmental correlations of +.47 and +.43. Compared with cigarette initiation and quantity of use in Norwegian twins, the role of genes was less prominent and shared environment more prominent for initiation and quantity of use of snus. Joint analyses of both tobacco phenotypes suggested, but did not confirm definitively, that genetic risk factors for cigarette and snus use were similar but not identical, while shared environmental factors existed that were specific to snus use.

• Kendler, Kenneth S.; Aggen, Steven H.; Gillespie, Nathan; Krueger, Robert F.; Czajkowski, Nikolai Olavi & Ystrøm, Eivind [Show all 7 contributors for this article] (2019). The structure of genetic and environmental influences on normative personality, abnormal personality traits, and personality disorder symptoms. Psychological Medicine. ISSN 0033-2917. 49(8), p. 1392–1399. doi: 10.1017/S0033291719000047. Full text in Research Archive
• Rosenström, Tom Henrik; Torvik, Fartein Ask; Ystrøm, Eivind; Czajkowski, Nikolai Olavi; Gillespie, Nathan A. & Aggen, Steven H. [Show all 9 contributors for this article] (2018). Prediction of alcohol use disorder using personality disorder traits: a twin study. Addiction. ISSN 0965-2140. 113(1), p. 15–24. doi: 10.1111/add.13951. Full text in Research Archive
• Lupattelli, Angela; Wood, Mollie; Ystrøm, Eivind; Skurtveit, Svetlana; Handal, Marte & Nordeng, Hedvig Marie Egeland (2018). Effect of Time-Dependent Selective Serotonin Reuptake Inhibitor Antidepressants During Pregnancy on Behavioral, Emotional, and Social Development in Preschool-Aged Children. Journal of the American Academy of Child and Adolescent Psychiatry. ISSN 0890-8567. 57(3), p. 200–208. doi: 10.1016/j.jaac.2017.12.010. Full text in Research Archive
• Harris, Gerd Marie Eskerud; Wood, Mollie; Ystrøm, Eivind & Nordeng, Hedvig Marie Egeland (2018). Prenatal triptan exposure and neurodevelopmental outcomes in 5-year-old children: Follow-up from the Norwegian Mother and Child Cohort Study. Paediatric and Perinatal Epidemiology. ISSN 0269-5022. 32(3), p. 247–255. doi: 10.1111/ppe.12461. Full text in Research Archive Show summary

  Background Triptans are commonly used to treat migraine headaches, but data on the long‐term safety of these medications during pregnancy are sparse. Triptans have a biologically plausible mechanism for effects on the fetal brain through binding to 5‐HT1‐receptors, and previous studies show increased risks of externalising behaviour problems in toddlers exposed to triptans during pregnancy. Methods We included 3784 children in the Norwegian Mother and Child Cohort Study, whose mothers returned the 5‐year‐questionnaire and reported a history of migraine or triptan use; 353 (9.3%) mothers reported use of triptans during pregnancy, 1509 (39.9%) reported migraine during pregnancy but no triptan use, and 1922 (50.8%) had migraine prior to pregnancy only. We used linear and log‐binomial models with inverse probability weights to examine the association between prenatal triptan exposure and internalising and externalising behaviour, communication, and temperament in 5‐year‐old children. Results Triptan‐exposed children scored higher on the sociability trait than unexposed children of mothers with migraine (β 1.66, 95% confidence interval [0.30, 3.02]). We found no other differences in temperament, or increased risk of behaviour or communication problems. Conclusions Contrary to results from previous studies in younger children, we found no increased risk of externalising behaviour problems in 5‐year‐old children exposed to triptans in fetal life. Triptan‐exposed children did have slightly more sociable temperaments, but the clinical meaning of this finding is uncertain.

• Rosenström, Tom Henrik; Gjerde, Line C.; Krueger, Robert Frederick; Aggen, Steven H.; Czajkowski, Nikolai Olavi & Gillespie, Nathan A. [Show all 10 contributors for this article] (2018). Joint factorial structure of psychopathology and personality. Psychological Medicine. ISSN 0033-2917. doi: 10.1017/S0033291718002982. Full text in Research Archive Show summary

  Background: Normative and pathological personality traits have rarely been integrated into a joint large-scale structural analysis with psychiatric disorders, although a recent study suggested they entail a common individual differences continuum. Methods: We explored the joint factor structure of 11 psychiatric disorders, five personality-disorder trait domains (DSM-5 Section III), and five normative personality trait domains (the ‘Big Five’) in a population-based sample of 2796 Norwegian twins, aged 19‒46. Results: Three factors could be interpreted: (i) a general risk factor for all psychopathology, (ii) a risk factor specific to internalizing disorders and traits, and (iii) a risk factor specific to externalizing disorders and traits. Heritability estimates for the three risk factor scores were 48% (95% CI 41‒54%), 35% (CI 28‒42%), and 37% (CI 31‒44%), respectively. All 11 disorders had uniform loadings on the general factor (congruence coefficient of 0.991 with uniformity). Ignoring sign and excluding the openness trait, this uniformity of factor loadings held for all the personality trait domains and all disorders (congruence 0.983). Conclusions: Based on our findings, future research should investigate joint etiologic and transdiagnostic models for normative and pathological personality and other psychopathology.

• Rosenqvist, Mina A.; Sjölander, Arvid; Ystrøm, Eivind; Larsson, Henrik & Reichborn-Kjennerud, Ted (2018). Adverse family life events during pregnancy and ADHD symptoms in five-year-old offspring. Journal of Child Psychology and Psychiatry. ISSN 0021-9630. doi: 10.1111/jcpp.12990. Full text in Research Archive Show summary

  Background Prenatal exposure to maternal adverse life events has been associated with offspring ADHD, but the role of familial confounding is unclear. We aimed to clarify if adverse life events during pregnancy are related to ADHD symptoms in offspring, taking shared familial factors into account. Method Data were collected on 34,751 children (including 6,427 siblings) participating in the population‐based Norwegian Mother and Child Cohort Study. During pregnancy, mothers reported whether they had experienced specific life events. We assessed ADHD symptoms in five‐year‐old children with the Conners’ Parent Rating Scale–Revised: short form. We modeled the associations between life events and mean ADHD scores with ordinary linear regression in the full cohort, and with fixed‐effect linear regression in sibling comparisons to adjust for familial confounding. Results Children exposed to adverse life events had higher ADHD scores at age 5, with the strongest effect observed for financial problems (mean differences 0.10 [95% CI: 0.09, 0.11] in adjusted model), and the weakest for having lost someone close (0.02 [95% CI 0.01, 0.04] in adjusted model). Comparing exposure‐discordant siblings resulted in attenuated estimates that were no longer statistically significant (e.g. mean difference for financial problems −0.03 [95% CI −0.07, 0.02]). ADHD scores increased if the mother had experienced the event as painful or difficult, and with the number of events, whereas sibling‐comparison analyses resulted in estimates attenuated toward the null. Conclusions These results suggest that the association between adverse life events during pregnancy and offspring ADHD symptoms is largely explained by familial factors.

• Gillespie, Nathan A.; Aggen, Steven H.; Neale, Michael C.; Knudsen, Gun Peggy S.; Krueger, Robert F. & South, Susan C. [Show all 11 contributors for this article] (2018). Associations between personality disorders and cannabis use and cannabis use disorder: a population‐based twin study. Addiction. ISSN 0965-2140. 113(8), p. 1488–1498. doi: 10.1111/add.14209. Full text in Research Archive
• Welander-Vatn, Audun; Torvik, Fartein Ask; Czajkowski, Nikolai Olavi; Kendler, Kenneth S; Reichborn-Kjennerud, Ted & Knudsen, Gun Peggy S. [Show all 7 contributors for this article] (2018). Relationships Among Avoidant Personality Disorder, Social Anxiety Disorder, and Normative Personality Traits: A Twin Study. Journal of Personality Disorders. ISSN 0885-579X. 33(3), p. 289–309. doi: 10.1521/pedi_2018_32_341. Full text in Research Archive
• Lupattelli, Angela; Rønningen, Elke; Krogsrud, Stine Kleppe; Nordeng, Hedvig Marie Egeland & Ystrøm, Eivind (2018). Personality and its relation to the use of alcohol and cigarettes during pregnancy: A multinational study. Journal of Health Psychology. ISSN 1359-1053. doi: 10.1177/1359105318775194. Full text in Research Archive Show summary

  This study explored the impact of women’s personality on drinking and smoking habits before and during pregnancy, using a multinational perspective. Data on maternal personality traits, background information, and alcohol and cigarette smoking before and during pregnancy were collected from 9187 women from more than 18 countries. High conscientiousness and agreeableness resulted as protective factors against alcohol consumption during pregnancy; trait-specific associations were apparent on individual region level. Highly extrovert women were more likely to consume medium/high amount of alcohol (10%–17% increased odds). High neuroticism conferred a 16 percent increased odds for continued smoking during pregnancy. Personality and nationality are important factors for adequate pre- and postnatal health care.

• Hannigan, Laurie J; Eilertsen, Espen Moen; Gjerde, Line C.; Reichborn-Kjennerud, Ted; Eley, Thalia C & Rijsdijk, Frühling V. [Show all 8 contributors for this article] (2018). Maternal prenatal depressive symptoms and risk for early-life psychopathology in offspring: genetic analyses in the Norwegian Mother and Child Birth Cohort Study. The Lancet Psychiatry. ISSN 2215-0374. 5(10), p. 808–815. doi: 10.1016/S2215-0366(18)30225-6. Full text in Research Archive Show summary

  Background. Maternal prenatal depression is a known risk factor for early-life psychopathology among offspring. However, it is necessary to distinguish between potential risk transmission mechanisms. We aimed to test the relative importance of passive genetic transmission, direct exposure, and indirect exposure in the association between maternal prenatal depressive symptoms and later internalizing and externalizing psychopathology. Methods. We used structural equation modelling of phenotypic data and genetically-informative relationships from the families of participants in the Norwegian Mother and Child Birth Cohort Study (MoBa). The analytic sub-sample of MoBa used in the current study comprises 22,195 mothers and 35,299 children. We used mothers’ self-reported depressive symptoms during pregnancy, as captured by the Symptom Checklist (SCL), and their reports of symptoms of psychopathology in their offspring during the first few years of life (measured at 18, 36, and 60 months using the Child Behavior Checklist [CBCL]). Findings. Maternal prenatal depressive symptoms were found to be associated with both internalizing and externalizing problems in early childhood primarily via intergenerationally-shared genetic factors. For internalizing problems, phenotypic transmission also contributed significantly to the association, but was found to be explained by exposure to concurrent maternal depressive symptoms, rather than by direct exposure. Interpretation. Associations between maternal prenatal depressive symptoms and offspring behavioral outcomes in early childhood are likely to be at least partially explained by shared genes. This genetic confounding should be considered when attempting to quantify risks posed by in utero exposure to maternal depressive symptoms.

• McAdams, Tom A; Hannigan, Laurie J; Eilertsen, Espen Moen; Gjerde, Line C.; Ystrøm, Eivind & Rijsdijk, Frühling V (2018). Revisiting the Children-of-Twins Design: Improving Existing Models for the Exploration of Intergenerational Associations. Behavior Genetics. ISSN 0001-8244. 48(5), p. 397–412. doi: 10.1007/s10519-018-9912-4. Full text in Research Archive Show summary

  Datasets comprising twins and their children can be a useful tool for understanding the nature of intergenerational associations between parent and offspring phenotypes. In the present article we explore structural equation models previously used to analyse Children-of-Twins data, highlighting some limitations and considerations. We then present new variants of these models, showing that extending the models to include multiple offspring per parent addresses several of the limitations discussed. Accompanying the updated models, we provide power calculations and demonstrate with application to simulated data. We then apply to intergenerational analyses of height and weight, using a sub-study of the Norwegian Mother and Child Cohort (MoBa); the Intergenerational Transmission of Risk (IToR) project, wherein all kinships in the MoBa data have been identified (a children-of-twins-and-siblings study). Finally, we consider how to interpret the findings of these models and discuss future directions.

• Ask, Helga; Gustavson, Kristin; Ystrøm, Eivind; Havdahl, Karoline Alexandra; Tesli, Martin Steen & Askeland, Ragna Bugge [Show all 7 contributors for this article] (2018). Association of Gestational Age at Birth With Symptoms of Attention-Deficit/Hyperactivity Disorder in Children. JAMA pediatrics. ISSN 2168-6203. 172(8), p. 749–756. doi: 10.1001/jamapediatrics.2018.1315. Full text in Research Archive
• Gillespie, Nathan A.; Aggen, Steven H.; Gentry, Amanda E.; Neale, Michael Churton; Knudsen, Gun Peggy S. & Krueger, Robert Frederick [Show all 14 contributors for this article] (2018). Testing Genetic and Environmental Associations Between Personality Disorders and Cocaine Use: A Population-Based Twin Study. Twin Research and Human Genetics. ISSN 1832-4274. 21(1), p. 24–32. doi: 10.1017/thg.2017.73. Full text in Research Archive Show summary

  Until now, data have not been available to elucidate the genetic and environmental sources of comorbidity between all 10 DSM-IV personality disorders (PDs) and cocaine use. Our aim was to determine which PD traits are linked phenotypically and genetically to cocaine use. Cross-sectional data were obtained in a face-to-face interview between 1999 and 2004. Subjects were 1,419 twins (µage = 28.2 years, range = 19–36) from the Norwegian Institute of Public Health Twin Panel, with complete lifetime cocaine use and criteria for all 10 DSM-IV PDs. Stepwise multiple and Least Absolute Shrinkage and Selection Operator (LASSO) regressions were used to identify PDs related to cocaine use. Twin models were fitted to estimate genetic and environmental associations between the PD traits and cocaine use. In the multiple regression, antisocial (OR = 4.24, 95% CI [2.66, 6.86]) and borderline (OR = 2.19, 95% CI [1.35, 3.57]) PD traits were significant predictors of cocaine use. In the LASSO regression, antisocial, borderline, and histrionic were significant predictors of cocaine use. Antisocial and borderline PD traits each explained 72% and 25% of the total genetic risks in cocaine use, respectively. Genetic risks in histrionic PD were not significantly related to cocaine use. Importantly, after removing criteria referencing substance use, antisocial PD explained 65% of the total genetic variance in cocaine use, whereas borderline explained only 4%. Among PD traits, antisocial is the strongest correlate of cocaine use, for which the association is driven largely by common genetic risks.

• Heiberg, Ina Heidi; Jacobsen, Bjarne K.; Nesvåg, Ragnar; Bramness, Jørgen Gustav; Reichborn-Kjennerud, Ted & Næss, Øyvind [Show all 9 contributors for this article] (2018). Total and cause-specific standardized mortality ratios in patients with schizophrenia and/or substance use disorder. PLOS ONE. 13(8). doi: 10.1371/journal.pone.0202028. Full text in Research Archive Show summary

  Individuals with schizophrenia or substance use disorder have a substantially increased mortality compared to the general population. Despite a high and probably increasing prevalence of comorbid substance use disorder in people with schizophrenia, the mortality in the comorbid group has been less studied and with contrasting results. We performed a nationwide open cohort study from 2009 to 2015, including all Norwegians aged 20–79 with schizophrenia and/or substance use disorder registered in any specialized health care setting in Norway, a total of 125,744 individuals. There were 12,318 deaths in the cohort, and total, sex-, age- and cause-specific standardized mortality ratios (SMRs) were calculated, comparing the number of deaths in patients with schizophrenia, schizophrenia only, substance use disorder only or a co-occurring diagnosis of schizophrenia and substance use disorder to the number expected if the patients had the age-, sex- and calendar-year specific death rates of the general population. The SMRs were 4.9 (95% CI 4.7–5.1) for all schizophrenia patients, 4.4 (95% CI 4.2–4.6) in patients with schizophrenia without substance use disorder, 6.6 (95% CI 6.5–6.8) in patients with substance use disorder only, and 7.4 (95% CI 7.0–8.2) in patients with both schizophrenia and substance use disorder. The SMRs were elevated in both genders, in all age groups and for all considered causes of death, and most so in the youngest. Approximately 27% of the excess mortality in all patients with schizophrenia was due to the raised mortality in the subgroup with comorbid SUD. The increased mortality in patients with schizophrenia and/or substance use disorder corresponded to more than 10,000 premature deaths, which constituted 84% of all deaths in the cohort. The persistent mortality gap highlights the importance of securing systematic screening and proper access to somatic health care, and a more effective prevention of premature death from external causes in this group.

• Degerud, Eirik; Ariansen, Inger Kristine Holtermann; Ystrøm, Eivind; Graff-Iversen, Sidsel; Høiseth, Gudrun & Mørland, Jørg [Show all 8 contributors for this article] (2018). Life course socioeconomic position, alcohol drinking patterns in midlife, and cardiovascular mortality: Analysis of Norwegian population-based health surveys. PLoS Medicine. ISSN 1549-1277. 15(1). doi: 10.1371/journal.pmed.1002476. Full text in Research Archive Show summary

  Background: Socioeconomically disadvantaged groups tend to experience more harm from the same level of exposure to alcohol as advantaged groups. Alcohol has multiple biological effects on the cardiovascular system, both potentially harmful and protective. We investigated whether the diverging relationships between alcohol drinking patterns and cardiovascular disease (CVD) mortality differed by life course socioeconomic position (SEP). Methods and findings: From 3 cohorts (the Counties Studies, the Cohort of Norway, and the Age 40 Program, 1987–2003) containing data from population-based cardiovascular health surveys in Norway, we included participants with self-reported information on alcohol consumption frequency (n = 207,394) and binge drinking episodes (≥5 units per occasion, n = 32,616). We also used data from national registries obtained by linkage. Hazard ratio (HR) with 95% confidence intervals (CIs) for CVD mortality was estimated using Cox models, including alcohol, life course SEP, age, gender, smoking, physical activity, body mass index (BMI), systolic blood pressure, heart rate, triglycerides, diabetes, history of CVD, and family history of coronary heart disease (CHD). Analyses were performed in the overall sample and stratified by high, middle, and low strata of life course SEP. A total of 8,435 CVD deaths occurred during the mean 17 years of follow-up. Compared to infrequent consumption (<once/month), moderately frequent consumption (2–3 times per week) was associated with a lower risk of CVD mortality (HR = 0.78, 95% CI 0.72, 0.84) overall. HRs for the high, middle, and low strata of SEP were 0.66 (95% CI 0.58, 0.76), 0.87 (95% CI 0.78, 0.97), and 0.79 (95% CI 0.64, 0.98), respectively, compared with infrequent users in each stratum. HRs for effect modification were 1.30 (95% CI 1.10, 1.54, p = 0.002; middle versus high), 1.23 (95% CI 0.96, 1.58, p = 0.10; low versus high), and 0.96 (95% CI 0.76, 1.21, p = 0.73; low versus middle). In the group with data on binge drinking, 2,284 deaths (15 years) from CVDs occurred. In comparison to consumers who did not binge during the past year, HRs among frequent bingers (≥1 time per week) were 1.58 (95% CI 1.31, 1.91) overall, and 1.22 (95% CI 0.84, 1.76), 1.71 (95% CI 1.31, 2.23), and 1.85 (95% CI 1.16, 2.94) in the strata, respectively. HRs for effect modification were 1.36 (95% CI 0.87, 2.13, p = 0.18; middle versus high), 1.63 (95% CI 0.92, 2.91, p = 0.10; low versus high), and 1.32 (95% CI 0.79, 2.20, p = 0.29; low versus middle). A limitation of this study was the use of a single measurement to reflect lifetime alcohol consumption. Conclusions: Moderately frequent consumers had a lower risk of CVD mortality compared with infrequent consumers, and we observed that this association was more pronounced among participants with higher SEP throughout their life course. Frequent binge drinking was associated with a higher risk of CVD mortality, but it was more uncertain whether the risk differed by life course SEP. It is unclear if these findings reflect differential confounding of alcohol consumption with health-protective or damaging exposures, or differing effects of alcohol on health across socioeconomic groups.

• Wang, Mari Vaage; Aarø, Leif Edvard & Ystrøm, Eivind (2018). Language Delay and Externalizing Problems in Preschool Age: A Prospective Cohort Study. Journal of Abnormal Child Psychology. ISSN 0091-0627. 46(5), p. 923–933. doi: 10.1007/s10802-017-0391-5. Full text in Research Archive
• Gjerde, Line C.; Eilertsen, Espen Moen; Eley, Thalia C.; McAdams, Tom A.; Reichborn-Kjennerud, Ted & Røysamb, Espen [Show all 7 contributors for this article] (2018). Maternal Perinatal and Concurrent Anxiety and Mental Health Problems in Early Childhood: A Sibling‐Comparison Study. Child Development. ISSN 0009-3920. doi: 10.1111/cdev.13192. Full text in Research Archive Show summary

  Do associations between maternal anxiety symptoms and offspring mental health remain after comparing differentially exposed siblings? Participants were 17,724 offspring siblings and 11,553 mothers from the Norwegian Mother and Child Cohort study. Mothers reported anxiety and depressive symptoms at 30 weeks’ gestation, and 0.5, 1.5, 3, and 5 years postpartum. Child internalizing and externalizing problems were assessed at ages 1.5, 3, and 5, and modeled using multilevel analyses with repeated measures nested within siblings, nested within mothers. Maternal pre‐ and postnatal anxiety were no longer associated with child internalizing or externalizing problems after adjusting for maternal depression and familial confounding. Maternal anxiety when the children were in preschool age, however, remained significantly associated with child internalizing but not externalizing problems.

• Vollrath, Margarete E.; Hampson, Sarah E.; Péneau, Sandrine; Rolland-Cachera, Marie Françoise & Ystrøm, Eivind (2018). Child temperament predicts the adiposity rebound. A 9-year prospective sibling control study. PLOS ONE. 13(11). doi: 10.1371/journal.pone.0207279. Full text in Research Archive Show summary

  The goal of this study is to examine the extent to which child temperament predicts the adiposity rebound, a steep increase in the body mass index (BMI) between ages 5 and 7 years. If this increase occurs at an earlier age, the risk for later obesity is elevated. To improve the accuracy of the examination, we use a genetically informed design, a sibling-control study, to control for genetic and familial confounding. We hypothesize that temperament traits tapping negative emotionality, approach and avoidance are associated with the adiposity rebound. Methods: We repeatedly examined 25889 siblings within the Norwegian Mother and Child Cohort Study, following them from the mothers’ pregnancy through child age 8 years. Information on the children’s height and weight was collected by means of health registries and maternal reports. Information on the siblings’ temperament was collected by questionnaires completed when they were 1.5, 3, and 5 years old. We examined the associations of temperament at different child ages with the timing of the adiposity rebound among siblings and controls by means of growth curve and multilevel analyses. Results: Within siblings, high scores on the approach trait of sociability predicted an earlier adiposity rebound and high scores on the avoidance trait of shyness predicted a later adiposity rebound with timing differences ranging between 6 and 16 weeks. Surprisingly, negative emotionality did not predict the adiposity rebound. The associations between temperament and the adiposity rebound increased with increasing child age. The results within controls—comparing siblings with the population, broadly paralleled those within siblings. Conclusions: The findings encourage the notion that child temperament functions as an early marker for the adiposity rebound. Future studies may advance our knowledge by including measures of child personality along the taxonomy of the adult Five Personality Factors.

• Eilertsen, Espen Moen; Gjerde, Line C.; Kendler, Kenneth S.; Røysamb, Espen; Aggen, Steven H. & Gustavson, Kristin [Show all 8 contributors for this article] (2018). Development of ADHD symptoms in preschool children: Genetic and environmental contributions. Development and Psychopathology. ISSN 0954-5794. 31(4), p. 1299–1305. doi: 10.1017/S0954579418000731. Full text in Research Archive Show summary

  We examined genetic and environmental contributions to the development of symptoms of attention-deficit/hyperactivity disorder (ADHD) in preschool children. ADHD symptoms in siblings at 1.5, 3, and 5 years of age were investigated in a population-based sample from the prospective Norwegian Mother and Child Cohort Study. The longitudinal contributions of additive genetic, shared, twin-specific, and unique environmental influences were estimated using biometric structural equation models. Heritability of ADHD symptoms ranged from 54% to 70%. There was evidence of partially new genetic influences at successive ages, with genetic correlations ranging from .58 to .89. Contributions from shared environmental factors and twin-specific factors were minor. The importance of unique environmental effects appeared to increase across ages, and was mostly specific to a given age. There was no evidence suggesting that this pattern differs across males and females. Symptoms of ADHD are highly heritability in young children from as early as 1.5 years of age. Longitudinal stability of ADHD symptoms is mainly attributable to genetic influences, but there is also some evidence for age-specific genetic influences. These findings contribute to our understanding of development of ADHD early in life, and can guide future molecular genetics studies.

• Torvik, Fartein Ask; Ystrøm, Eivind; Gustavson, Kristin; Rosenström, Tom Henrik; Bramness, Jørgen Gustav & Gillespie, N [Show all 9 contributors for this article] (2018). Diagnostic and genetic overlap of three common mental disorders in structured interviews and health registries. Acta Psychiatrica Scandinavica. ISSN 0001-690X. 137(1), p. 54–64. doi: 10.1111/acps.12829. Full text in Research Archive Show summary

  Objective: To investigate whether diagnostic data from structured interviews, primary care and specialist care registries on major depressive disorder (MDD), anxiety disorders (AD) and alcohol use disorder (AUD) identify the same individuals, yield comparable comorbidity estimates and reflect the same genetic influences. Methods: Registry data from primary and specialist care were available for 11 727 twins and diagnostic interview data for 2271 of these. We used logistic regression analyses and biometric modelling to investigate the overlap between the data sources. Results: Most individuals meeting diagnostic criteria at interview were not registered with a corresponding diagnosis. The rates of registration were higher for MDD (36% in primary care and 15% in specialist care) and AD (21% and 18%) than for AUD (3% and 7%). Comorbidity estimated as odds ratios, but not as polychoric correlations, was higher in the registries than in the interviews. Genetic influences on the disorders were highly correlated across data sources (median r = 0.81), bordering unity for MDD and AD. Conclusion: Prevalence and comorbidity estimates differ between registries and population‐based assessment. Nevertheless, diagnoses from health registries reflect the same genetic influences as common mental disorders assessed in the general population, indicating generalizability of aetiological factors across data sources.

• Torvik, Fartein Ask; Gustavson, Kristin; Ystrøm, Eivind; Rosenström, Tom Henrik; Gillespie, Nathan & Reichborn-Kjennerud, Ted [Show all 7 contributors for this article] (2018). Continuity of genetic and environmental influences on clinically assessed major depression from ages 18 to 45. Psychological Medicine. ISSN 0033-2917. p. 1–9. doi: 10.1017/S0033291718003550. Full text in Research Archive
• Holdø, Ingvild; Bramness, Jørgen Gustav; Handal, Marte; Torgersen, Leila; Reichborn-Kjennerud, Ted & Ystrøm, Eivind [Show all 8 contributors for this article] (2017). Hypnotics use in children 0-18 months: moderate agreement between mother-reported survey data and prescription registry data. Journal of Pharmaceutical Policy and Practice. 10:28, p. 1–8. doi: 10.1186/s40545-017-0117-7. Full text in Research Archive Show summary

  Background Different methods in pharmacoepidemiology can be used to study hypnotic use in children. But neither questionnaire-based data nor prescription records can be considered a “gold standard”. This study aimed to investigate the agreement between mother-reported questionnaire-based data and prescription record data for hypnotic drugs in children aged 0–18 months. The agreement was compared to the agreement for a group of antiepileptic drugs. Methods Prescription record data were collected from the Norwegian prescription database for 47,413 children also surveyed in the Norwegian mother and child cohort between 2005 and 2009. Agreement between in the two data sources was calculated using Cohens Kappa. Multinomial logistic regression was used to calculate the effect of sociodemographic variables on discrepancies in data sources. Results The agreement between mother-reported and dispensed hypnotics was less than 50% for all hypnotics. Sensitivity of reporting increased with number of filled prescriptions. The agreement of antiepileptic drugs was 92.9% in the same population. Of several sociodemographic factors only paternal educational level and maternal work situation was significantly related to agreement between prescription record and survey data. Conclusion There was a moderate agreement between reported use and dispensed hypnotic drugs for infants and toddlers. Results indicate that sociodemographic factors play only a minor role in explaining discrepancy.

• Kendler, Kenneth S; Aggen, Steven H; Gillespie, Nathan; Neale, Michael C; Knudsen, Gun Peggy & Krueger, Robert F [Show all 9 contributors for this article] (2017). The Genetic and Environmental Sources of Resemblance Between Normative Personality and Personality Disorder Traits. Journal of Personality Disorders. ISSN 0885-579X. 31(2), p. 193–207. doi: 10.1521/pedi_2016_30_251. Full text in Research Archive
• Nesvåg, Ragnar; Reichborn-Kjennerud, Ted; Gillespie, Nathan; Knudsen, Gun Peggy; Bramness, Jørgen Gustav & Kendler, Kenneth S [Show all 7 contributors for this article] (2017). Genetic and Environmental Contributions to the Association Between Cannabis Use and Psychotic-Like Experiences in Young Adult Twins. Schizophrenia Bulletin. ISSN 0586-7614. 43(3), p. 644–653. doi: 10.1093/schbul/sbw101. Full text in Research Archive
• Long, Elizabeth C.; Aggen, Steven H.; Neale, Michael Churton; Knudsen, Gun Peggy; Krueger, Robert Frederick & South, Susan Carol [Show all 13 contributors for this article] (2017). The association between personality disorders with alcohol use and misuse: A population-based twin study. Drug and Alcohol Dependence. ISSN 0376-8716. 174, p. 171–180. doi: 10.1016/j.drugalcdep.2017.01.022. Full text in Research Archive
• Reichborn-Kjennerud, Ted; Krueger, R F; Ystrøm, Eivind; Torvik, Fartein Ask; Rosenström, Tom Henrik & Aggen, S H [Show all 11 contributors for this article] (2017). Do DSM-5 Section II personality disorders and Section III personality trait domains reflect the same genetic and environmental risk factors? Psychological Medicine. ISSN 0033-2917. 47(12), p. 2205–2215. doi: 10.1017/S0033291717000824. Full text in Research Archive
• Abel, Marianne Hope; Ystrøm, Eivind; Caspersen, Ida Henriette; Meltzer, Helle Margrete; Aase, Heidi & Torheim, Liv Elin [Show all 9 contributors for this article] (2017). Maternal iodine intake and offspring attention-deficit/hyperactivity disorder: Results from a large prospective cohort study. Nutrients. 9(11). doi: 10.3390/nu9111239. Full text in Research Archive Show summary

  Current knowledge about the relationship between mild to moderately inadequate maternal iodine intake and/or supplemental iodine on child neurodevelopment is sparse. Using information from 77,164 mother-child pairs in the Norwegian Mother and Child Cohort Study, this study explored associations between maternal iodine intake and child attention-deficit/hyperactivity disorder (ADHD) diagnosis, registered in the Norwegian Patient Registry and maternally-reported child ADHD symptoms at eight years of age. Pregnant women reported food and supplement intakes by questionnaire in gestational week 22. In total, 1725 children (2.2%) were diagnosed with ADHD. In non-users of supplemental iodine (53,360 mothers), we found no association between iodine intake from food and risk of child ADHD diagnosis (p = 0.89), while low iodine from food (<200 µg/day) was associated with higher child ADHD symptom scores (adjusted difference in score up to 0.08 standard deviation (SD), p < 0.001, n = 19,086). In the total sample, we found no evidence of beneficial effects of maternal use of iodine-containing supplements (n = 23,804) on child ADHD diagnosis or symptom score. Initiation of iodine supplement use in gestational weeks 0–12 was associated with an increased risk of child ADHD (both measures). In conclusion, insufficient maternal iodine intake was associated with increased child ADHD symptom scores at eight years of age, but not with ADHD diagnosis. No reduction of risk was associated with maternal iodine supplement use.

• Brandlistuen, Ragnhild Eek; Ystrøm, Eivind; Hernandez-Diaz, Sonia; Skurtveit, Svetlana; Selmer, Randi & Handal, Marte [Show all 7 contributors for this article] (2017). Association of prenatal exposure to benzodiazepines and child internalizing problems: A sibling-controlled cohort study. PLOS ONE. 12(7). doi: 10.1371/journal.pone.0181042. Full text in Research Archive Show summary

  Background: During pregnancy, many women experience sleep problems and anxiety that require treatment. The long-term safety for the child of maternal benzodiazepine (BZD) and z-hypnotic use during pregnancy remains controversial. Method: We conducted a cohort and a sibling control study using data from the Norwegian Mother and Child Cohort Study. Data on use of BZD and z-hypnotics, internalizing and externalizing outcomes, and covariates were collected from mothers at gestational weeks 17 and 30 and when children were 0.5, 1.5, and 3 years of age. The total sample consisted of 71,996 children (19,297 siblings) at 1.5 years and 55,081 children (13,779 siblings) at 3 years. Short-term use was defined as use in one pregnancy period only. Long-term use was defined as use in two or more pregnancy periods. Linear full cohort random-effect and sibling-matched fixed-effect regression models were used to compare internalizing and externalizing behavior in children prenatally exposed compared to those unexposed in the full cohort of pregnancies accounting for family clusters, as well as within sibling clusters comparing pregnancies with discordant exposures. Propensity score (PS) adjustment included variables on indication for use (sleep problems, symptoms of anxiety and depression) and other potential confounding factors. Results: Long-term prenatal exposure to BZD or z-hypnotics was associated with increased internalizing behavior in crude cohort analyses and at age 1.5 years after PS adjustment in sibling-matched fixed-effect models [β 0.60, 95% confidence interval 0.17–0.95]. Analyses on specific drug groups showed that prenatal exposure to BZD-anxiolytics was associated with increased internalizing problems at both 1.5 years [β 0.25, 0.01–0.49] and 3 years [β 0.26, 0.002–0.52] while exposure to z-hypnotics was not associated with any adverse outcomes after adjustment. Conclusion: The findings suggest a moderate association between BZD-anxiolytic exposure and child internalizing problems that is not likely due to stable familial confounding factors.

• Ystrøm, Eivind; Hysing, Mari; Torgersen, Leila; Ystrøm, Hilde Thorsen; Reichborn-Kjennerud, Ted & Sivertsen, Børge (2017). Maternal Symptoms of Anxiety and Depression and Child Nocturnal Awakenings at 6 and 18 Months. Journal of Pediatric Psychology. ISSN 0146-8693. 42(10), p. 1156–1164. doi: 10.1093/jpepsy/jsx066. Full text in Research Archive
• South, Susan C; Krueger, Robert F; Knudsen, Gun Peggy; Ystrøm, Eivind; Czajkowski, Nikolai Olavi & Aggen, Steven H [Show all 10 contributors for this article] (2017). A Population Based Twin Study of DSM–5 Maladaptive Personality Domains. Personality Disorders: Theory, Research, and Treatment. ISSN 1949-2715. 8(4), p. 366–375. doi: 10.1037/per0000220. Full text in Research Archive
• Degerud, Eirik; Ystrøm, Eivind; Tambs, Kristian; Ariansen, Inger Kristine; Mørland, Jørg & Magnus, Per [Show all 8 contributors for this article] (2017). The interplay between cognitive ability, alcohol consumption, and health characteristics. Psychological Medicine. ISSN 0033-2917. 48(12), p. 2011–2022. doi: 10.1017/S0033291717003543. Full text in Research Archive
• Rosenström, Tom Henrik; Ystrøm, Eivind; Torvik, Fartein Ask; Czajkowski, Nikolai Olavi; Gillespie, Nathan A. & Aggen, Steven H. [Show all 9 contributors for this article] (2017). Genetic and Environmental Structure of DSM-IV Criteria for Antisocial Personality Disorder: A Twin Study. Behavior Genetics. ISSN 0001-8244. 47(3), p. 265–277. doi: 10.1007/s10519-016-9833-z. Full text in Research Archive
• Eilertsen, Espen Moen; Gjerde, Line C.; Reichborn-Kjennerud, Ted; Ørstavik, Ragnhild; Knudsen, Gun Peggy & Stoltenberg, Camilla [Show all 10 contributors for this article] (2017). Maternal alcohol use during pregnancy and offspring attention-deficit hyperactivity disorder (ADHD): a prospective sibling control study. International Journal of Epidemiology. ISSN 0300-5771. 46(5), p. 1633–1640. doi: 10.1093/ije/dyx067. Full text in Research Archive Show summary

  Background: Maternal alcohol use during pregnancy has repeatedly been associated with development of attention-deficit hyperactivity disorder (ADHD) in the offspring. It is, however not known whether this reflects a direct casual intra-uterine effect or a non-causal relationship due to confounding. We used three different approaches to control for measured and unmeasured confounding: statistical adjustment for covariates, negative control comparison against maternal pre-pregnancy alcohol use, and comparison among differentially exposed siblings. Methods: The sample comprised 114 247 children (34 283 siblings) from 94 907 mothers, recruited to the Norwegian Mother and Child Birth Cohort Study between 1999 and 2008. Self-reported measurements of alcohol use were obtained in week 30 during the pregnancy. Mothers rated offspring ADHD symptoms at 5 years on two measures. Clinical ADHD diagnoses were obtained from the Norwegian Patient Registry. Results: We found an overall positive association between maternal alcohol use during pregnancy and offspring ADHD symptoms, which was only marginally attenuated after inclusion of measured covariates. Both the negative control and the sibling comparison analysis further attenuated the estimated association, but it remained greater than zero [ β  = 0.017, 95% confidence interval (CI) = 0.005–0.030). No association was found between maternal alcohol use during pregnancy and offspring ADHD diagnosis. Conclusions: For offspring ADHD symptoms we found a weak, but possibly causal association with maternal alcohol use during pregnancy, but no such effect was observed for clinical ADHD diagnosis.

• Gjerde, Line C.; Eilertsen, Espen Moen; Reichborn-Kjennerud, Ted; McAdams, Tom A.; Zachrisson, Henrik Daae & Zambrana, Imac Maria [Show all 9 contributors for this article] (2017). Maternal perinatal and concurrent depressive symptoms and child behavior problems: a sibling comparison study. Journal of Child Psychology and Psychiatry. ISSN 0021-9630. 58(7), p. 779–786. doi: 10.1111/jcpp.12704. Full text in Research Archive Show summary

  Background: Previous studies have found significant associations between maternal prenatal and postpartum depression and child behavior problems (CBP). The present study investigates whether associations remain in a prospective, longitudinal design adjusted for familial confounding. Methods: The sample comprised 11,599 families including 17,830 siblings from the Norwegian Mother and Child Cohort study. Mothers reported depressive symptoms at gestational weeks 17 and 30, as well as 6 months, 1.5, 3, and 5 years postpartum. Fathers’ depression was measured at gestational week 17. At the last three time-points, child internalizing and externalizing problems were concurrently assessed. We performed multilevel analyses for internalizing and externalizing problems separately, using parental depression as predictors. Analyses were repeated using a sibling comparison design to adjust for familial confounding. Results: All parental depressive time-points were significantly and positively associated with child internalizing and externalizing problems. After sibling comparison, however, only concurrent maternal depression was significantly associated with internalizing [estimate = 2.82 (1.91–3.73, 95% CI)] and externalizing problems [estimate = 2.40 (1.56–3.23, 95% CI)]. The effect of concurrent maternal depression on internalizing problems increased with child age. Conclusions: Our findings do not support the notion that perinatal maternal depression is particularly detrimental to children's psychological development, as the most robust effects were found for maternal depression occurring during preschool years.

• Gustavson, Kristin; Ystrøm, Eivind; Stoltenberg, Camilla; Susser, Ezra; Surén, Pål & Magnus, Per [Show all 12 contributors for this article] (2017). Smoking in pregnancy and child ADHD. Pediatrics. ISSN 0031-4005. 139(2). doi: 10.1542/peds.2016-2509. Full text in Research Archive
• Ystrøm, Eivind; Gustavson, Kristin; Brandlistuen, Ragnhild Eek; Knudsen, Gun Peggy; Magnus, Per & Susser, Ezra [Show all 14 contributors for this article] (2017). Prenatal exposure to acetaminophen and risk of ADHD. Pediatrics. ISSN 0031-4005. 140:20163840(5), p. 1–11. doi: 10.1542/peds.2016-3840. Full text in Research Archive
• Gervin, Kristina; Nordeng, Hedvig Marie Egeland; Ystrøm, Eivind; Reichborn-Kjennerud, Ted & Lyle, Robert (2017). Long-term prenatal exposure to paracetamol is associated with DNA methylation differences in children diagnosed with ADHD. Clinical Epigenetics. 9. doi: 10.1186/s13148-017-0376-9. Full text in Research Archive Show summary

  Background: Epidemiological studies have shown that long-term exposure to paracetamol during pregnancy is associated with attention-deficit/hyperactivity disorder (ADHD). The mechanism by which paracetamol may modulate the increased risk of developing ADHD is currently unknown. We have conducted an epigenome-wide association study (n = 384 cord blood samples) and investigated whether prenatal exposure to paracetamol is associated with DNA methylation in children diagnosed with ADHD. Results: Analyses identified significant differences in DNA methylation (n = 6211 CpGs) associated with prenatal exposure to paracetamol for more than 20 days in children diagnosed with ADHD compared to controls. In addition, these samples were differentially methylated compared to samples with ADHD exposed to paracetamol for less than 20 days (n = 2089 CpGs) and not exposed to paracetamol (n = 193 CpGs). Interestingly, several of the top genes ranked according to significance and effect size have been linked to ADHD, neural development, and neurotransmission. Gene ontology analysis revealed enrichment of pathways involved in oxidative stress, neurological processes, and the olfactory sensory system, which have previously been implicated in the etiology of ADHD. Conclusions: These initial findings suggest that in individuals susceptible to ADHD, prenatal long-term exposure to paracetamol is associated with DNA methylation differences compared to Controls.

• Ystrøm, Hilde Thorsen; Nilsen, Wendy; Hysing, Mari; Sivertsen, Børge & Ystrøm, Eivind (2017). Sleep Problems in Preschoolers and Maternal Depressive Symptoms: An Evaluation of Mother- and Child-Driven Effects. Developmental Psychology. ISSN 0012-1649. 53(12), p. 2261–2272. doi: 10.1037/dev0000402. Full text in Research Archive
• Torvik, Fartein Ask; Rosenström, Tom Henrik; Ystrøm, Eivind; Tambs, Kristian; Røysamb, Espen & Czajkowski, Nikolai Olavi [Show all 10 contributors for this article] (2017). Stability and change in etiological factors for alcohol use disorder and major depression. Journal of Abnormal Psychology. ISSN 0021-843X. 126(6), p. 812–822. doi: 10.1037/abn0000280. Full text in Research Archive Show summary

  Alcohol use disorder (AUD) and major depressive disorder (MDD) are often comorbid. It is not understood how genetic risk factors for these disorders relate to each other over time and to what degree they are stable. Age-dependent characteristics of the disorders indicate that different genetic factors could be relevant at different stages of life, and MDD may become increasingly correlated with AUD over time. DSM–IV diagnoses of AUD and MDD were assessed by interviews of 2,801 young adult twins between 1999 and 2004 (T1) and 2,284 of the same twins between 2010 and 2011 (T2). Stability, change, and covariation were investigated in longitudinal biometric models. New genetic factors explained 56.4% of the genetic variance in AUD at T2. For MDD, there was full overlap between genetic influences at T1 and T2. Genetic risk factors for MDD were related to AUD, but their association with AUD did not increase over time. Thus, genetic risk factors for AUD, but not MDD, vary with age, suggesting that AUD has age-dependent heritable etiologies. Molecular genetic studies of AUD may therefore benefit from stratifying by age. The new genetic factors in AUD were not related to MDD. Environmental influences on the 2 disorders were correlated in middle, but not in young adulthood. The environmental components for AUD correlated over time (r = .27), but not for MDD. Environmental influences on AUD can have long-lasting effects, and the effects of preventive efforts may be enduring. Environment influences seem to be largely transient.

• Ystrøm, Eivind; Ørstavik, Ragnhild; Reichborn-Kjennerud, Ted & Torvik, Fartein Ask (2016). Social inequalities in reception of social welfare support: A population based twin study. Norsk Epidemiologi. ISSN 0803-2491. 26(1-2), p. 57–62. doi: 10.5324/nje.v26i1-2.2016. Full text in Research Archive Show summary

  Social welfare support runs in families. Recent studies using Nordic registry data have found individual differences in genetic factors to be of substantial importance for medical benefits. However, to date there has been no genetically informative studies on receiving social welfare support. To prevent young adults to not drop out of the work life and become recipients of social welfare support, it is of substantial interest to clarify to what extent the familiarity of social welfare support is due to genetic or social differences between families. We used data from the Historical-Event Database on 7,698 Norwegian twins born 1967-1979 to estimate the relative contribution of genetic factors, the effective familial environment (i.e. the “shared environment”), and individual-specific environmental factors. We found that the two forms of familial risk, genetic and shared environmental, explained 39% and 45%, respectively, of the risk for receiving social welfare support among young Norwegian twins. Only 17% of the variance in risk factors could be explained by individual-specific risk factors. It appears that risk for receiving social welfare support can to a great extent be explained by environmental differences between families. Therefore prevention strategies targeting social inequalities between families would indeed be effective. Furthermore, genetic risk factors are also important in explaining risk for receiving social welfare support. These effects could be mediated through heritable traits related to substance abuse, psychiatric disorders, and personality. Individual-specific risk factors were of very little importance. Hence, with regard to receiving social welfare support, family matters.

• Vatn, Audun Svendsen; Ystrøm, Eivind; Tambs, Kristian; Neale, MC; Kendler, KS & Reichborn-Kjennerud, Ted [Show all 7 contributors for this article] (2016). The relationship between anxiety disorders and dimensional representations of DSM-IV personality disorders: A co-twin control study. Journal of Affective Disorders. ISSN 0165-0327. 190, p. 349–356. doi: 10.1016/j.jad.2015.09.038. Full text in Research Archive
• Nezvalova-Henriksen, Katerina; Spigset, Olav; Brandlistuen, Ragnhild Eek; Ystrøm, Eivind; Koren, Gideon & Nordeng, Hedvig Marie Egeland (2016). Effect of prenatal selective serotonin reuptake inhibitor (SSRI) exposure on birthweight and gestational age: a sibling-controlled cohort study. International Journal of Epidemiology. ISSN 0300-5771. 45(6), p. 2018–2029. doi: 10.1093/ije/dyw049. Full text in Research Archive
• Torvik, Fartein Ask; Reichborn-Kjennerud, Ted; Gjerde, Line C.; Knudsen, Gun Peggy; Ystrøm, Eivind & Tambs, Kristian [Show all 9 contributors for this article] (2016). Mood, anxiety, and alcohol use disorders and later cause-specific sick leave in young adult employees. BMC Public Health. 16. doi: 10.1186/s12889-016-3427-9. Full text in Research Archive Show summary

  Background Mental disorders strongly influence work capability in young adults, but it is not clear which disorders that are most strongly associated with sick leave, and which diagnoses that are stated on the sick leave certificates. Better knowledge of the impairments associated with different mental disorders is needed for optimal planning of interventions and prioritization of health services. In the current study, we investigate the prospective associations between eight mood, anxiety, and alcohol use disorders, and later sick leave granted for mental, somatic, or any disorder. Methods Lifetime mental disorders were assessed by structured diagnostic interviews in 2,178 young adults followed for eight years with registry data on sick leave. Relative risk ratios were estimated for the associations between each mental disorder and the different forms of sick leave. Results All included diagnoses were associated with later sick leave. In adjusted analyses, major depressive disorder and generalized anxiety disorder were the strongest predictors of sick leave granted for mental disorders, whereas social anxiety disorder and specific phobia were the strongest predictors of sick leave granted for somatic disorders. Specific phobia and major depressive disorder had the highest attributable fractions for all-cause sick leave. Conclusions Mood and anxiety disorders constituted independent risk factors for all cause sick leave, whereas alcohol use disorders seemed to be of less importance in young adulthood. Disorders characterised by distress were most strongly associated with sick leave granted for mental disorders, whereas disorders characterised by fear primarily predicted sick leave granted for somatic conditions. A large part of all sick leave is related to specific phobia, due to the high prevalence of this disorder. The impairment associated with this common disorder may be under-acknowledged, and it could decrease work capacity among individuals with somatic disorders. This disorder has good treatment response and may be overlooked as a target for interventions aimed at prevention of sick leave.

• Zambrana, Imac Maria; Vollrath, Margarete E.; Sengpiel, Verena; Jacobsson, Bo & Ystrøm, Eivind (2016). Preterm delivery and risk for early language delays: A sibling-control cohort study. International Journal of Epidemiology. ISSN 0300-5771. 45(1), p. 151–159. doi: 10.1093/ije/dyv329. Full text in Research Archive
• Torvik, Fartein Ask; Vatn, Audun Svendsen; Ystrøm, Eivind; Knudsen, Gun Peggy; Czajkowski, Nikolai Olavi & Kendler, Kenneth S. [Show all 7 contributors for this article] (2016). Longitudinal Associations Between Social Anxiety Disorder and Avoidant Personality Disorder: A Twin Study. Journal of Abnormal Psychology. ISSN 0021-843X. 125(1), p. 114–124. doi: 10.1037/abn0000124. Full text in Research Archive
• Juch, Herbert; Lupattelli, Angela; Ystrøm, Eivind; Verheyen, Sarah & Nordeng, Hedvig Marie Egeland (2016). Medication adherence among pregnant women with hypothyroidism—missed opportunities to improve reproductive health? A cross-sectional, web-based study. Patient Education and Counseling. ISSN 0738-3991. 99(10), p. 1699–1707. doi: 10.1016/j.pec.2016.04.006. Full text in Research Archive
• Østby, Kristian Amundsen; Czajkowski, Nikolai Olavi; Knudsen, Gun Peggy; Ystrøm, Eivind; Gjerde, Line C. & Kendler, Kenneth S. [Show all 8 contributors for this article] (2016). Does low alcohol use increase the risk of sickness absence? A discordant twin study. BMC Public Health. 16. doi: 10.1186/s12889-016-3502-2. Full text in Research Archive Show summary

  Background Results from observational studies suggest that people who drink little or no alcohol are less healthy than medium drinkers. This has been demonstrated for many different measures of health, including sick leave. However, whether these associations are causal or due to confounding remains to be clarified. The aim of this study was to use a discordant twin design to determine whether the increased level of sick leave associated with a low level of alcohol consumption, as compared to those with a medium level of consumption, reflects a causal mechanism or is due to genetic or environmental confounding. Methods Six thousand seven hundred thirty-four young adult twins from the Norwegian Institute of Public Health’s twin panel were in 1998 assessed for frequency of alcohol use and binge drinking. Data were linked to the Norwegian National Insurance Administration’s recordings of sick leave over a 10 year period. The associations between alcohol consumption and sick leave were first estimated in the total study population, and then within di- and monozygotic twin pairs discordant for alcohol use. Results Compared to medium consumption, both low and high alcohol consumption was associated with increased risk of sick leave. When low level drinkers were compared to medium level drinkers in a discordant twin design, the results were consistent with the association being due to genetic confounding rather than a causal effect. Conclusions The increased level of sick leave observed with low level drinkers seems to be mainly explained by confounding from genetic factors. In all observational studies of the relationship between alcohol consumption and health, one should be aware that important genetic confounders are likely to influence the results.

• Wood, Mollie; Lapane, Kate; Frazier, Jean A; Ystrøm, Eivind; Mick, Eric O & Nordeng, Hedvig Marie Egeland (2016). Prenatal Triptan Exposure and Internalising and Externalising Behaviour Problems in 3-Year-Old Children: Results from the Norwegian Mother and Child Cohort Study. Paediatric and Perinatal Epidemiology. ISSN 0269-5022. 30(2), p. 190–200. doi: 10.1111/ppe.12253. Full text in Research Archive
• Magnusson, Karin; Scurrah, Katrina J.; Ystrøm, Eivind; Ørstavik, Ragnhild; Nilsen, Thomas Sevenius & Steingrímsdóttir, Ólöf Anna [Show all 10 contributors for this article] (2016). Genetic factors contribute more to hip than knee surgery due to osteoarthritis - a population-based twin registry study of joint arthroplasty. Osteoarthritis and Cartilage. ISSN 1063-4584. 25(6), p. 878–884. doi: 10.1016/j.joca.2016.12.015. Full text in Research Archive
• Kendler, Kenneth S.; Aggen, SH; Neale, MC; Knudsen, Gun Peggy; Krueger, Robert F & Tambs, Kristian [Show all 10 contributors for this article] (2015). A longitudinal twin study of cluster A personality disorders. Psychological Medicine. ISSN 0033-2917. 45(7), p. 1531–1538. doi: 10.1017/S0033291714002669. Full text in Research Archive
• Knudsen, Ann Kristin; Ystrøm, Eivind; Skogen, Jens Christoffer & Torgersen, Leila (2015). Maternal heavy alcohol use and toddler behavior problems: a fixed effects regression analysis. European Child and Adolescent Psychiatry. ISSN 1018-8827. 24(10), p. 1269–1277. doi: 10.1007/s00787-015-0677-5. Full text in Research Archive Show summary

  Using data from the longitudinal Norwegian Mother and Child Cohort Study, the aims of the current study were to examine associations between postnatal maternal heavy alcohol use and toddler behavior problems, taking both observed and unobserved confounding factors into account by employing fixed effects regression models. Postnatal maternal heavy alcohol use (defined as drinking alcohol 4 or more times a week, or drinking 7 units or more per alcohol use episode) and toddler internalizing and externalizing behavior problems were assessed when the toddlers were aged 18 and 36 months. Maternal psychopathology, civil status and negative life events last year were included as time-variant covariates. Maternal heavy alcohol use was associated with toddler internalizing and externalizing behavior problems (p < 0.001) in the population when examined with generalized estimating equation models. The associations disappeared when observed and unobserved sources of confounding were taken into account in the fixed effects models [(p = 0.909 for externalizing behaviors (b = 0.002, SE = 0.021), p = 0.928 for internalizing behaviors (b = 0.002, SE = 0.023)], with an even further reduction of the estimates with the inclusion of time-variant confounders. No causal effect was found between postnatal maternal heavy alcohol use and toddler behavior problems. Increased levels of behavior problems among toddlers of heavy drinking mothers should therefore be attributed to other adverse characteristics associated with these mothers, toddlers and families. This should be taken into account when interventions aimed at at-risk families identified by maternal heavy alcohol use are planned and conducted.

• Sivertsen, Børge; Harvey, Allison G.; Reichborn-Kjennerud, Ted; Torgersen, Leila; Ystrøm, Eivind & Hysing, Mari (2015). Later Emotional and Behavioral Problems Associated With Sleep Problems in Toddlers. A Longitudinal Study. JAMA pediatrics. ISSN 2168-6203. 169(6), p. 575–582. doi: 10.1001/jamapediatrics.2015.0187. Full text in Research Archive
• Reichborn-Kjennerud, Ted; Czajkowski, Nikolai Olavi; Ystrøm, Eivind; Ørstavik, Ragnhild; Aggen, Steven H. & Tambs, Kristian [Show all 12 contributors for this article] (2015). A longitudinal twin study of borderline and antisocial personality disorder traits in early to middle adulthood. Psychological Medicine. ISSN 0033-2917. 45(14), p. 3121–3131. doi: 10.1017/S0033291715001117. Full text in Research Archive
• Torgersen, Leila; Ystrøm, Eivind; Siega-Riz, Anna Maria; Knoph, Cecilie; Zerwas, Stephanie & Reichborn-Kjennerud, Ted [Show all 7 contributors for this article] (2015). Maternal eating disorder and infant diet. A latent class analysis based on the Norwegian Mother and Child Cohort Study (MoBa). Appetite. ISSN 0195-6663. 84, p. 291–298. doi: 10.1016/j.appet.2014.10.009. Full text in Research Archive

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• Ystrom, Eivind; Timpe, Clara Marie Fides & Jole, Oda van (2027). Sosial ulikhet i Norge og barns psykiske utvikling - en megakobling. Full text in Research Archive
• Smajlagic, Dinka; Sunde, Hans Fredrik; Valenza-Troubat, Noemie; Kelly, Kristen; Lyu, Xuanyu & Sapin, Emmanuel [Show all 12 contributors for this article] (2026). Estimating assortative mating using haplotype-specific polygenic scores across physiological, psychological, and social traits in the Norwegian MoBa Cohort. doi: https:/s3.amazonaws.com/ClubExpressClubFiles/971921/documents/BGA_2026_Final_Program_1883376854.pdf?AWSAccessKeyId=AKIA6MYUE6DNCQ7GISON&Expires=1790839847&response-content-disposition=inline%3B%20filename%3DBGA_2026_Final_Program.pdf&Signature=nfauyWIWzAanx8Du1HeYli1Hi0Q%3D. Full text in Research Archive
• Madhavan, Vaishnavi K; Demange, Perline Aline Delle; Ayorech, Ziada; Hottenga, Jouke Jan; Bartels, Meike & Ystrom, Eivind [Show all 8 contributors for this article] (2026). Bipolar Disorder and Education: Deciphering a Complex Relationship using Genetic and Sibling Differences. doi: https:/s3.amazonaws.com/ClubExpressClubFiles/971921/documents/BGA_2026_Final_Program_1883376854.pdf?AWSAccessKeyId=AKIA6MYUE6DNCQ7GISON&Expires=1790839847&response-content-disposition=inline%3B%20filename%3DBGA_2026_Final_Program.pdf&Signature=nfauyWIWzAanx8Du1HeYli1Hi0Q%3D. Full text in Research Archive
• Demange, Perline Aline Delle; Akingbuwa, Wonuola; Cheesman, Rosa Catherine Gillespie & Ystrom, Eivind (2026). A Genomic Test of Goodness-of-Fit: Using Personality Polygenic Indices to Model Parent–Child Fit during Development. Full text in Research Archive
• Demange, Perline Aline Delle; Cheesman, Rosa Catherine Gillespie; Akingbuwa, Wonuola & Ystrom, Eivind (2026). A Genomic Test of Goodness-of-Fit: Using Personality Polygenic Indices to Model Parent–Child Fit. Full text in Research Archive
• Tabori, Mia; Enander, Hilda; Ystrom, Eivind & Demange, Perline Aline Delle (2026). To What Extent Does Early Temperament Predict Symptoms of Anxiety and Depression in Adolescence? A Sibling Design. Full text in Research Archive
• Ofstad, Sverre Berg; Peng, Qiyuan; Ebeltoft, Joakim; Bjørndal, Ludvig Daae; Rayner, Christopher & Ayorech, Ziada [Show all 10 contributors for this article] (2026). PGI-by-Environment interactions: practical guidelines for robust research. Full text in Research Archive
• Ivanova, Anna & Ystrom, Eivind (2026). Temporal relationships between dysmenorrhea and depression in Norwegian women. Full text in Research Archive
• Ystrom, Eivind & Torvik, Fartein Ask (2026). How to study GxE in schools. Full text in Research Archive
• Ystrom, Eivind; Demange, Perline Aline Delle; Cheesman, Rosa Catherine Gillespie; McAdams, Thomas Andrew; Eilertsen, Espen Moen & Timpe, Clara Marie Fides [Show all 8 contributors for this article] (2026). Child Personality Polygenic Indices and Parental Distress: Evidence of Active Gene-Environment Correlations and Interactions from Parent–Offspring Trios. doi: https:/osf.io/fwaqp/overview. Full text in Research Archive Show summary

  Child temperament and personality are conjectured to affect parental distress, and there are findings supporting such transactions. Yet, to date, there is no evidence for such evocative gene-environment correlations using exogenous within-family offspring genetic variation. Using 30 000 parent–offspring genotyped trios from the Norwegian Mother, Father and Child Cohort (MoBa), we test how child personality polygenic indexes (PGIs) independently affect maternal and paternal mental distress across the life course (age 16-60). The second longstanding hypothesis is that such child-to-parent transactions are non-additive due to gene-environment interactions. We will reveal the scope of this by estimating the expansion of within-person-timepoint parental mental distress over child personality PGIs. The third longstanding hypothesis is that the evocative effect is dependent on the parental personality, or the “goodness-of-fit”. We will examine moderation by parental Big Five PGIs to test if the effect of a child’s personality on parent depression depends on the parent’s own personality predispositions. This genetically controlled approach provides a novel and robust test of child- evoked effects across the life course. Results for both mothers and fathers will be presented, highlighting the power of child PGIs as a new tool to reveal intergenerational influences on parental mental distress.

• Ystrom, Eivind (2026). Disentangling Direct and Indirect Genetic Effects on Complex Traits: Insights from Two Large-Scale Family Studies. doi: https:/bga.org/docs.ashx?id=1781704. Full text in Research Archive
• Ystrom, Eivind; Ayorech, Ziada; Bjørndal, Ludvig Daae; Timpe, Clara Marie Fides; Cheesman, Rosa Catherine Gillespie & Eilertsen, Espen Moen [Show all 8 contributors for this article] (2026). Child Personality Polygenic Indices and Parental Distress: Evidence of Active Gene- Environment Correlations and Interactions from Parent–Offspring Trios. doi: https:/bga.org/docs.ashx?id=1781704. Full text in Research Archive
• Ystrom, Eivind (2026). Da Mette og Helle ble gravide, ble de en snakkis blant helsepersonell. [Journal]. Aftenposten. Full text in Research Archive Show summary

  Dette er helt tilfeldig og ganske usannsynlig. Men de eneggede tvillingene Mette og Helle Bugge Bergsund (36) har selv fått hvert sitt par eneggede tvillinger i løpet av tre måneder.

• Ystrom, Eivind (2026). Are You Mostly Noise? Eivind Ystrøm on the Genetics of Personality. doi: https:/www.podbean.com/ew/pb-x24tj-1a9abb6. Full text in Research Archive Show summary

  Personality psychologists were doing behavior genetics way before it was cool. In this episode, Rafael and Aysu sit down with Eivind Ystrøm, personality psychologist at the University of Oslo, to talk about what personality actually is, how heritable it turns out to be, and why the field was so far ahead of the rest of the social sciences in taking genetics seriously. They also dig into one of the most provocative findings in the field: the so-called "gloomy prospect" — the idea that a large chunk of what makes you you may come down to essentially random, non-systematic events that even siblings growing up in the same household don't share. What does this mean for the search for specific environmental causes of personality? And more importantly — what is the mysterious mutation that Eivind thinks he may have?

• Ystrom, Eivind & Ivanova, Anna (2026). Do reproductive factors shape depression stability? Early menarche, endometriosis and PMS in longitudinal registry data. doi: https:/2026.ehps.net/wp-content/uploads/2026/08/ehps26_final_program_27_08-1.pdf. Full text in Research Archive Show summary

  Background: Menstrual and gynaecological conditions may increase depression risk, but it is unclear whether they relate to onset versus persistence. Methods: 85,637 women aged 14 to 72 from the Norwegian Mother, Father and Child Cohort Study (MoBa) contributed with 18,415,809 person-months of patient registry data (2006–2023) on primary-care depression diagnosis. Early menarche (before age 12), endometriosis, and Premenstrual Syndrome (PMS) was recorded by questionnaire. Log-binomial regression was used to estimate risk ratios (RR) for population average effects and conditioned on prior-month depression to additionally test condition*prior-depression (stability) interactions and condition*age interactions. Results: Depression was prevalent in 26.3% of women across the 18-year observation period and incident within 1.18% of the person-months. Early menarche, endometriosis, and PMS predicted higher depression risk RR=1.22 (95%CI 1.15-1.29), 1.19 (95%CI 1.04-1.36), and 1.68 (95%CI 1.61-1.75). Conditioning on prior month depression status, main effects were for early menarche RR=1.21 (95%CI 1.15-1.28), endometriosis RR=1.19 (95%CI 1.04-1.35), and PMS remained RR=1.70 (95%CI 1.63-1.77); indicating associations were primarily with transitions into depression rather than persistence. Early menarche RR=0.83 (95%CI 0.79-0.88), endometriosis RR=0.83 (95%CI 0.72-0.95), and PMS RR=0.59 (95%CI 0.56-0.61) all contributed to lower stability of depression. Furthermore, early menarche gave a diminishing risk for depression with older age. Conclusions: Early menarche, endometriosis, and PMS mark elevated depression burden. However, this appears to happen primarily through increased transitions into depression rather than chronicity. Hence, early age of menarche, endometriosis, and PMS may help identify women eligible for preventive mental health interventions rather than being fixed markers of life-course depression risk.

• Ystrom, Eivind (2026). No Link Between Acetaminophen in Pregnancy and Autism, a Study Finds. [Journal]. The New York Times. doi: https:/www.nytimes.com/2026/01/16/health/tylenol-autism-acetaminophen-study.html. Full text in Research Archive Show summary

  The review looked at more than three dozen studies and found no evidence that acetaminophen increased the risk of neurodevelopmental disorders in children.

• Ystrom, Eivind & Madsen, Ole Jacob (2026). Fritt hjemme, strengt på skolen. [Internet]. forskning.no. Full text in Research Archive Show summary

  Dagens foreldre skaper problemer på skolen, ifølge lærere. Professor mener vi overdriver effekten av foreldrestiler.

• Ystrom, Eivind (2026). Ny studie tilbakeviser Trumps Paracet-teori. [Internet]. tv2. Full text in Research Archive Show summary

  USAs president påstod at risikoen for utvikling av autisme økte ved mors inntak av paracetamol.

• ofstad, Sverre; Demange, Perline; Qin, Qi; Cheesman, Rosa; Torvik, Fartein Ask & Ystrom, Eivind (2026). How Schools Can Narrow the Gender and Genetic Gaps in Educational Achievement. Research Square. ISSN 2693-5015. doi: 10.21203/rs.3.rs-8592276/v1. Full text in Research Archive Show summary

  Abstract Boys have received lower average grades than girls for over a century, with likely implications for their future educational opportunities, mental health, and mortality. However, there are also considerable achievement differences within both gender groups, largely owing to individual differences in cognitive and non-cognitive skills. Identifying mechanisms within schools that shape educational gaps related to both gender and skills could reveal approaches to support all struggling students, regardless of gender. We computed polygenic indices for cognitive and non-cognitive skills for a sample of 36,800 Norwegian students across 1,068 lower secondary schools, leveraging genetic variation as an exogenous source of student skills through a within-family design. By interacting the polygenic indices with gender and a wide range of population-representative school environments, we find that some school environments provide additional benefits for students with lower non-cognitive predispositions. This compensatory support was especially pronounced for boys. Additionally, while both gender groups benefited from the same school environments, effects were generally larger for boys. Taken together, our results indicate that schools may reduce educational achievement differences within and across gender groups by reducing the influence of non-cognitive predispositions on achievement.

• Qin, Qi; Demange, Perline Aline Delle; Eilertsen, Espen Moen; Cheesman, Rosa Catherine Gillespie & Ystrom, Eivind (2026). How Schools and Neighborhoods Shape the Translation of Polygenic Personality Indices into Academic Outcomes. Full text in Research Archive Show summary

  The Big Five personality traits are robust predictors of individual differences in academic outcomes, yet the mechanisms through which they shape the outcomes remain unclear. Building on our prior work showing contextual moderation of non-cognitive polygenic indices (PGI), we hypothesize that personality traits likewise do not exert uniform influences across contexts. Instead, their effects on academic outcomes emerge through dynamic interactions with the social and economic environments in which individuals develop. Recent GWAS on Big Five personality traits enable the construction of PGIs that quantify the individual-level genetic propensities, and are largely independent of the environment and minimize reverse causality. Using data from ~32,000 trios in the Norwegian Mother, Father, and Child Cohort Study (MoBa) linked to national school and residential registries, we apply multilevel models to investigate how personality-related PGIs contribute to students’ grade point average (GPA), and how these associations vary across latent school and neighborhood contexts. We further test the extent to which the measured socioeconomic status aggregates at the school and neighborhood level interact with individual liability in personality traits. This work aims to provide a comprehensive framework for understanding how individual propensities for personality become developmentally expressed into academic outcomes within real-world contextual ecologies.

• Peng, Qiyuan; Rietveld, Cornelius A.; Ystrom, Eivind; Zachrisson, Henrik Daae; Havdahl, Alexandra & Cheesman, Rosa Catherine Gillespie (2026). Does Universal Childcare Affect Early Child Development? Full text in Research Archive
• Ofstad, Sverre Berg; Demange, Perline Aline Delle; Ayorech, Ziada; Valstad, Mathias & Ystrom, Eivind (2026). Temporal Trends in the Severity and Impairment of Childhood and Adolescent ADHD: A Population-Wide Genetic Study in Norway. Full text in Research Archive Show summary

  By calculating family genetic risk scores for the entire for the entire Norwegian population for birth years 1992-2019, ages 6-16 (N ≈ 1.5M) we show that the reduction in functional impairment over time is largely attributed to a diagnostic expansion of less genetically severe cases. Those who are diagnosed today have lower levels of genetic risk, while simulatenously, there has been no change in the relationship between GPA at age 16 and genetic risk for ADHD.

• Bjørndal, Ludvig Daae; Valstad, Mathias; Eilertsen, Espen Moen; Ayorech, Ziada; Ofstad, Sverre Berg & Salvatore, Jessica E. [Show all 8 contributors for this article] (2026). Peer effects contribute to psychiatric disorder risk: A population-wide study. Full text in Research Archive
• Ofstad, Sverre Berg; Demange, Perline Aline Delle; Ayorech, Ziada; Valstad, Mathias & Ystrom, Eivind (2026). Temporal Trends in the Severity and Impairment of Childhood and Adolescent ADHD: A Population-Wide Genetic Study in Norway. Full text in Research Archive Show summary

  By calculating family genetic risk scores for the entire for the entire Norwegian population for birth years 1992-2019, ages 6-16 (N ≈ 1.5M) we show that the reduction in functional impairment over time is largely attributed to a diagnostic expansion of less genetically severe cases. Those who are diagnosed today have lower levels of genetic risk, while simulatenously, there has been no change in the relationship between GPA at age 16 and genetic risk for ADHD.

• Fang, Yuan; Ystrom, Eivind; Eftedal, Nikolai Haahjem; Edvoll, Maud Clemson; Folstad, Siri Hausland & Røysamb, Espen [Show all 10 contributors for this article] (2026). Socioeconomic Differences in Student Mental Health Following a Nationwide Curriculum Reform. Full text in Research Archive
• Edvoll, Maud Clemson; Folstad, Siri Hausland; Eftedal, Nikolai Haahjem; Poornikoo, Mehdi; Fang, Yuan & Ystrom, Eivind [Show all 11 contributors for this article] (2026). Conference poster; A Norwegian curriculum reform: Effects for 10th graders’ academic performance. Full text in Research Archive
• Yang, Tianfang; Eftedal, Nikolai Haahjem; Valstad, Mathias; Reichborn-Kjennerud, Ted; Ystrom, Eivind & Czajkowski, Nikolai Olavi (2025). The lifespan impact of personality disorder on marital outcome: a Norwegian population study. Full text in Research Archive
• Czajkowski, Nikolai Olavi; Gustavson, Kristin & Ystrom, Eivind (2025). When Dracula Takes the PID-5: What Can We Learn from Psychometric Exploration of Data Simulated Using Large Language Models. Full text in Research Archive Show summary

  Several recent studies have demonstrated that large language models (LLMs) are able to simulate responses to surveys in ways that mimic observed characteristics of data from real human samples (Argyle, 2023). Since LLMs are trained on a sizeable proportion of all text produced by humans, it is reasonable to expect that they capture a deep understanding of human personality traits. Consequently, analysing data simulated by LLM’s may enable new ways to study psychological constructs and develop psychometric instruments. In this exploratory study, we used the GPT programming interface (API) to prompt the model to generate responses for 300 well-known literary characters across several instruments related to pathological and normative personality traits. This included the PID-5, the Structured Interview for DSM-5 Personality Disorders (SIDP), the Big Five Inventory-2 (BFI-2), and the IPIP-300. Characters were drawn from a wide range of literary traditions, genres, and historical periods. For each instrument, GPT-4o was instructed to adopt the voice and perspective of the character and provide item-level responses using standard Likert-style scales. Our goal was twofold: first, to assess whether the factor structures and inter-scale correlations observed in the simulated data resembled those from real-world samples; and second, to explore whether the same data might suggest novel trait constellations or latent domains not fully captured by existing instruments. Together, these analyses offer a proof of concept for using LLMs in hypothesis generation and instrument development.

• Ystrom, Eivind (2025). Forsker | Utdanning.no. [Internet]. utdanning.no. Full text in Research Archive Show summary

  – Du må stå opp hver dag og faktisk ha lyst til å drive med forskning, forteller Eivind.

• Ystrom, Eivind (2025). Paracetamol under graviditet forårsaker ikke autisme eller ADHD. [Journal]. VG. Full text in Research Archive Show summary

  Norsk studie av 100 000 barn viser ingen årsakssammenheng.

• Ystrom, Eivind (2025). FHI beroliger: Ingen påvist sammenheng mellom paracetamol hos gravide og autisme hos barn. [Journal]. Sykepleien. doi: https:/sykepleien.no/2025/11/fhi-beroliger-ingen-pavist-sammenheng-mellom-paracetamol-hos-gravide-og-autisme-hos-barn. Full text in Research Archive
• Ystrom, Eivind (2025). Fagprat på fredag med Eivind Ystrøm: Sammenhengen mellom genetikk og skoleprestasjoner - Senter for spesialpedagogisk forskning og inkludering (SpedAims). Full text in Research Archive Show summary

  De fleste kjenner til at utfordringer som dysleksi, matematikkvansker og ADHD ofte har en arvelig komponent. Men det er mindre intuitivt at også hvordan vi presterer i fag som norsk og matematikk generelt kan være påvirket av genetiske faktorer gjennom arvbare trekk – ikke bare av sosial bakgrunn. I denne fagpraten presenterer Eivind Ystrøm, professor i personlighetspsykologi og leder for genetikkgruppen ved PROMENTA Research Centre (GeoGen), ny kunnskap om hvordan arv og miljø virker sammen i barns utvikling. Ystrøm forsker på hvordan genetiske og miljømessige faktorer former tidlig sosioøkonomisk utvikling og psykisk helse, blant annet gjennom slektskapsstudier og molekylærgenetiske analyser. Forskningen hans omfatter også «genetic nurture» – hvordan foreldres arvelige egenskaper påvirker barns utvikling, selv når barna ikke arver de samme genene – og hvordan genetiske effekter varierer på tvers av skoler og nærmiljøer.

• Fang, Yuan; Ystrom, Eivind; Eftedal, Nikolai Haahjem; Poornikoo, Mehdi; Edvoll, Maud & Folstad, Siri Hausland [Show all 11 contributors for this article] (2025). Differential Effects of a Nationwide Curriculum-Based Intervention on Student Mental Health: The Role of Socioeconomic Status. doi: 10.17605/OSF.IO/3J6FY. Full text in Research Archive
• Ystrom, Eivind (2025). Writing and Publishing: Reflections from JCPP Advances Editors (Eivind Ystrøm). [Internet]. The Association for Child and Adolescent Mental Health. doi: 10.13056/acamh.13851. Full text in Research Archive Show summary

  In this video from the Writing and Publishing: Reflections from JCPP Advances Editors series, Professor Eivind Ystrøm discusses how unstructured thinking time can lead to creative scientific insights. He reflects on using dialectic reasoning and narrative techniques drawn from film to engage readers and shape research arguments. Drawing on personal habits and storytelling, he shares how self-imposed constraints can support productivity and encourages early-career researchers to view the review process as a constructive dialogue. Learning Objectives 1. Recognise how unstructured time and everyday routines can foster research creativity. 2. Understand how dialectic reasoning and narrative techniques can be used to engage readers. 3. Reframe the peer review process as a dialogue with editors and reviewers.

• Valstad, Mathias; Eftedal, Nikolai Haahjem; Yang, Tianfang; Reichborn-Kjennerud, Ted; Ystrom, Eivind & Czajkowski, Nikolai Olavi (2025). Epidemiology of personality disorders in Norway, 2010 to 2022. Full text in Research Archive
• Ystrøm, Eivind & Nordeng, Hedvig Marie Egeland (2025). Paracetamol i svangerskapet. Tidsskrift for Den norske legeforening (Tidsskriftet). ISSN 0029-2001. 145(14), p. 1164–1164. doi: 10.4045/tidsskr.25.0645. Full text in Research Archive
• Czajkowski, Nikolai Olavi; Eilertsen, Espen Moen; Valstad, Mathias; Eftedal, Nikolai Haahjem & Ystrøm, Eivind (2025). A Bayesian Framework for Zygosity Classification and Heritability Estimation Using Nationwide Registry Data. Full text in Research Archive
• Ystrøm, Eivind (2025). Intevju om helseråd til gravide. [TV]. Tv2 Nyhetskanalen. Full text in Research Archive
• Porneso, Ralph Pascual Ortiz; Havdahl, Alexandra; Eilertsen, Espen Moen & Ystrøm, Eivind (2025). Genetic Non-Additivity Reveals Variants in Complex Traits. doi: https:/geneforum.ee/wp-content/uploads/2025/09/Gene-Forum-Poster-Abstract-book.pdf. Full text in Research Archive Show summary

  Background: The contribution of non-additive genetic variation in human traits is nil for dominance, small for epistasis and, theory suggests, minimal for gene-environment interaction. Evidence from behavioral genetics indicates genetic interactions play a role in cognitive traits, and recent genome-wide association studies (GWAS) on height and BMI have identified single nucleotide polymorphisms (SNPs) involved in interactions. This study is a first step to uncover the molecular mechanisms behind gene-gene and gene- environment interactions and, in part, bridge the gap in the missing heritability problem. Study question: Are there SNPs associated with complex traits plasticity? Methods: We used a non-linear mixed effects framework to concurrently estimate SNPs’ mean (i.e. additive) and within individual variability (i.e. non-additive) effects on height and BMI at 6, 8 and 12 months (N=~45,000) and Math and Reading scores at grades 5, 8 and 9 (N=~65,000) from the Norwegian Mother Father and Child cohort (MoBa). We compared our models against a newly developed pipeline, trajGWAS, which restricts discovery to variants with linear within subject (WS) variance effects. Our approach relaxes this restriction. In addition, we investigated whether time-varying effects overlap with non- additive effects. Main results: We found putative “plasticity” variants with linear and non-linear effects. We provide within-individual variability summary statistics for height, BMI, Math and Reading. We found SNP time-varying effects explain ~1% of non-additive effects on average but found no overlap. Limitations: At present, our pipeline runs only using multiple cores and takes a considerable amount of compute hours.

• Porneso, Ralph Pascual Ortiz; Havdahl, Alexandra; Eilertsen, Espen Moen & Ystrøm, Eivind (2025). Non-additive genetic effects and complex traits plasticity. Full text in Research Archive Show summary

  Genome-wide association studies (GWAS) on educational attainment and related outcomes have succeeded at identifying hundreds to thousands of genetic variants with small additive effects using measures collected at a single time point. Recently, GWAS leveraging measures collected at multiple time points have found novel genetic associations, suggesting the presence of previously undetected time-specific variants. We hypothesized that a subset of these variants may be involved in gene-by-gene or gene-by-environment interaction. In the present study, we expanded the GWAS framework by estimating genetic effects on the residual variance. We used non-linear mixed effects (NLME) and double generalized linear models (DGLM) to concurrently estimate mean and within individual variance effects on academic performance in Math and Reading at grades 5, 8 and 9 in ~65,000 children from the Norwegian Mother Father and Child cohort (MoBa). We compared our models against a newly developed pipeline, trajGWAS, which restricts variant discovery to those with log-linear within subject (WS) variance effects. Our approach does not impose this restriction and found variants with non-linear variance effect. We replicated findings from other variance-based approaches that non-additive effects co-occur with mean effects. We decorrelated these effects and provide summary statistics for Math and Reading. This study is a first step to better understanding gene-by-gene and gene-by-environment interactions and shed light on the genetic correlates and potential mechanisms involved in complex trait plasticity.

• Eilertsen, Espen Moen; Ayorech, Ziada Ng'ombo Laurel; Cheesman, Rosa Catherine Gillespie & Ystrøm, Eivind (2025). Et mangfold av ulikhet: Fra økonomi til gener. Full text in Research Archive
• Ayorech, Ziada Ng'ombo Laurel & Ystrøm, Eivind (2025). Genes, Providers, and Depression: Expanding the Scope of Psychiatric Genetic Epidemiology to the Patient–Clinician Relationship. Full text in Research Archive
• Ayorech, Ziada Ng'ombo Laurel & Ystrøm, Eivind (2025). Reflections of an early career researcher. Full text in Research Archive
• Ofstad, Sverre Berg; Demange, Perline Aline Delle; Torvik, Fartein Ask; Cheesman, Rosa Catherine Gillespie; Qin, Qi & Ystrøm, Eivind (2025). Using within-family polygenic indexes to examine sex-specific gene-environment interaction on GPA. Full text in Research Archive
• Ystrøm, Eivind (2025). Genes as environments – intergenerational transmission of mental health. Full text in Research Archive
• Ystrøm, Eivind (2025). Intergenerational transmission of mental health in the Norwegian Mother, Father and Child Cohort study. Full text in Research Archive
• Ystrøm, Eivind (2025). Parent-Child Fit for Physical Education: Variance Modeling Reveals Independent Pathways. Full text in Research Archive
• Ystrøm, Eivind (2025). There has never been a cause and effect relationship established between Tylenol/Paracetamol/Acetaminophen and autism. [Internet]. Instagram. doi: https:/www.instagram.com/reel/DO8Ln00DGyO/?utm_source=ig_web_copy_link&igsh=MzRlODBiNWFlZA%3D%3D. Full text in Research Archive Show summary

  Acetaminophen is considered the only safe over the counter option for pain or fever for pregnant people. My morning fact check.

• Ystrøm, Eivind (2025). Debate Flares Over an Unproven Link Between Tylenol and Autism. [Journal]. The New York Times. Full text in Research Archive Show summary

  Studies over the last decade of acetaminophen use in pregnancy — including a recent scientific review — have yielded mixed results but have not found a causal connection.

• Ystrøm, Eivind (2025). Trump links Tylenol with autism despite evidence it's safe. [TV]. CNN International. doi: https:/uio-my.sharepoint.com/:v:/g/personal/eivindy_uio_no/Ee-39d2grOxEvlwMibPt0YcBGi8cenLBv5Ctc1Y-m9t0Kw?e=q6537F. Full text in Research Archive
• Ystrøm, Eivind (2025). Norsk forsker om Trumps paracetamol-påstand: - Kan bli alvorlig. [Internet]. tv2.no. Full text in Research Archive Show summary

  - Jeg blir bekymret av uttalelsene fordi Paracet er det mest anbefalte medikamentet å bruke når en har feber under graviditeten, sier forsker Eivind Ystrøm.

• Peng, Qiyuan; Rietveld, Cornelius A. (Niels); Cheesman, Rosa Catherine Gillespie; Ystrøm, Eivind & Havdahl, Alexandra (2025). Causal Intergenerational Transmission of Education in Norway. Full text in Research Archive
• Peng, Qiyuan; Eilertsen, Espen Moen; Cheesman, Rosa Catherine Gillespie; Rietveld, Cornelius A. (Niels); Ystrøm, Eivind & Havdahl, Alexandra (2025). Parental Influence on Children's Educational Achievements: Analysing Direct and Indirect Genetic Effects through Trio-GCTA. doi: https:/www.sv.uio.no/psi/english/research/news-and-events/events/conferences/2025/genetics-and-social-sciences-conference--2025.html. Full text in Research Archive
• Peng, Qiyuan; Pettersen, Johanne Hagen; Sunde, Hans Fredrik; Rietveld, Cornelius A. (Niels); Cheesman, Rosa Catherine Gillespie & Demange, Perline Aline Delle [Show all 11 contributors for this article] (2025). Intergenerational Transmission of Education in Norway: A Triangulation Approach. Full text in Research Archive
• Peng, Qiyuan; Pettersen, Johanne Hagen; Sunde, Hans Fredrik; Rietveld, Cornelius A. (Niels); Cheesman, Rosa Catherine Gillespie & Demange, Perline Aline Delle [Show all 11 contributors for this article] (2025). Intergenerational Transmission of Education in Norway: A Triangulation Approach. Full text in Research Archive Show summary

  The intergenerational transmission of education is a critical topic in social science. Substantial empirical evidence shows that children of highly educated parents often achieve higher levels of academic success than those of less-educated parents (Blanden et al., 2024; Björklund and Salvanes, 2011). Both environmental and genetic factors contribute to the association between parental and offspring educational attainment. However, existing empirical research often conflates these effects due to methodological differences and data limitations, making the results challenging to interpret and sometimes yielding conflicting conclusions (Atav et al., 2024). These limitations restrict insights to intergenerational correlations rather than establishing causal effects. Our study addresses this gap by employing a triangulation approach, integrating multiple methods with distinct strengths and biases to examine whether parental education causally impacts offspring’s educational achievement. Specifically, by leveraging parent-child trios’ register data from Statistics Norway and genetic data from the Norwegian Mother, Father, and Child Cohort Study (MoBa), we apply multivariable regression analysis, entropy balancing, adoption design, and within-family Mendelian randomization to explore the causal relationship between parental educational attainment and offspring’s educational achievement (grade point average, GPA) in Norway. Our preliminary findings suggest a causal effect of parental educational attainment on offspring’s academic success during adolescence, with variations between maternal and paternal influences and differential effects by offspring sex. By isolating genetic confounders, this study enhances our understanding of the causal pathways in intergenerational educational transmission, offering valuable insights for addressing educational inequalities.

• Porneso, Ralph Pascual Ortiz; Havdahl, Alexandra; Eilertsen, Espen Moen & Ystrøm, Eivind (2025). Genetic non-additivity reveals variants in complex traits plasticity. Full text in Research Archive Show summary

  In human complex traits, the contribution of non-additive relative to additive genetic variation is nil (dominance) to small (genetic interactions) which makes variant discovery difficult to achieve (Hivert, 2018). Even with larger samples, gene-gene and gene-environment interaction studies face several technical challenges (e.g. greater multiple testing burden, collecting and modelling correlated factors, etc) that impede progress in uncovering biological insights behind trait plasticity . We work around these issues by concurrently modelling the effect of single nucleotide polymorphisms (SNPs) on trait level, which shifts the distribution, and variability, which generates heteroscedasticity (unequal variance across genotype levels) resulting in the spreading out of phenotypic values around a mean. This approach does not require explicit interaction terms to be fitted to the data thereby lessening both computational complexity and multiple testing burden encountered by more traditional approaches. We estimate SNP effects on trait level (additive) and variability (non-additive) using a longitudinal heteroscedastic mixed effects model that assume uncorrelated variance components. In total, we found 25 lead putative plasticity SNPs (i.e. 2 for infant length, 11 for BMI, 5 for math and 7 for reading) of which 5 (1 for infant length and 4 for BMI) were previously reported in epistatic or gene-environment interaction in independent studies. We show that non-additive, time-varying and additive effects are correlated with each other across all 4 traits, indicating additive genetic variation captures SNP interaction effects. Our findings provide SNP-based evidence that non-additive genetic variation contributes to complex traits including height.

• Ayorech, Ziada Ng'ombo Laurel; Cheesman, Rosa Catherine Gillespie; Demange, Perline Aline Delle; Eilertsen, Espen Moen; Valstad, Mathias & Ystrøm, Eivind (2025). How the importance of family history and gender for receiving a depression diagnosis varies over GP’s. Full text in Research Archive
• Ayorech, Ziada Ng'ombo Laurel; Cheesman, Rosa Catherine Gillespie; Demange, Perline Aline Delle; Eilertsen, Espen Moen & Ystrøm, Eivind (2025). Leveraging family-based data reveals gene-environment interplay in life course depression. Full text in Research Archive
• Rayner, Chris; Mcadams, Tom; Havdahl, Alexandra; Ystrøm, Eivind & Ayorech, Ziada Ng'ombo Laurel (2025). A repeated measures GWAS in relatives: detecting age-specific genetic effects on maternal depression. Full text in Research Archive
• Ayorech, Ziada Ng'ombo Laurel & Ystrøm, Eivind (2025). Social Media as a Communication Tool. Full text in Research Archive
• Demange, Perline Aline Delle; Eilertsen, Espen Moen & Ystrøm, Eivind (2025). Beyond trio: genetic effects in the entire extended family. Full text in Research Archive
• Ystrøm, Eivind (2025). Gener har nesten alt å si for IQ, ifølge studie. – Kanskje skal vi spørre hvorfor vi belønner de med høy IQ så mye. [Internet]. forskning.no. Full text in Research Archive
• Demange, Perline Aline Delle; Eilertsen, Espen Moen & Ystrøm, Eivind (2025). Beyond trio: genetic effects in the extended family. Full text in Research Archive
• Ofstad, Sverre Berg; Demange, Perline Aline Delle; Cheesman, Rosa Catherine Gillespie; Qin, Qi; Torvik, Fartein Ask & Ystrøm, Eivind (2025). from DNA to GPA: a genetically informed study of the male disadvantage in schools. Full text in Research Archive
• Yang, Tianfang; Ystrøm, Eivind; Valstad, Mathias; Eftedal, Nikolai Haahjem; Reichborn-Kjennerud, Ted & Czajkowski, Nikolai Olavi (2025). Marital Consequence of Personality Disorder: Evidence from Norwegian Registry. Full text in Research Archive
• Eilertsen, Espen Moen; Cheesman, Rosa Catherine Gillespie; Ayorech, Ziada Ng'ombo Laurel & Ystrøm, Eivind (2024). Parent SES and young people's mental health. Full text in Research Archive
• Cheesman, Rosa Catherine Gillespie; Eilertsen, Espen Moen; Ayorech, Ziada Ng'ombo Laurel; Ystrøm, Eivind; Hootegem, Arno Van & Lyngstad, Torkild Hovde (2024). Parent SES and offspring mental health. Full text in Research Archive
• Ayorech, Ziada Ng'ombo Laurel; Cheesman, Rosa Catherine Gillespie; Demange, Perline Aline Delle; Eilertsen, Espen Moen; Valstad, Mathias & Ystrøm, Eivind (2024). GEOGRAPHICAL STRATIFICATION IN RECEIVING A DEPRESSION DIAGNOSIS IN THE NORWEGIAN POPULATION. doi: https:/www.sciencedirect.com/science/article/abs/pii/S0924977X24005455. Full text in Research Archive Show summary

  Background Depression runs in families, has a striking female preponderance, and in 2030 is predicted to be the leading cause of disease burden worldwide. Receiving a depression diagnosis is critical for access to appropriate treatment to alleviate the debilitating symptoms associated with this common disorder. Evidence that patient characteristics can contribute to who receives a diagnosis is well documented, however the extent to which GP tendencies for diagnosing depression are geographically stratified is unknown, in part due to the sparsity of large scale diagnostic data in population cohorts. Methods Here we capitalize on registry data for ∼ 5 million Norwegian adults including all ICPC2 depression codes, GP, clinic and residential identifiers. Multilevel models are used to test whether the role of familial risk (i.e., affected siblings) in predicting diagnosis varies as a function of geographical location and GP characteristics. In addition we test whether GP diagnosing varies by patients genetic risk and self-report symptoms by adding depression polygenic scores and symptom checklist data for a subset of the population (200,000 genotyped participants in the Norwegian Mother Father and Child study (Moba)) to our models. Results We provide descriptions of depression clusters across the entire Norwegian country and critical insight into the path from symptoms to diagnosis. Crucially, this novel approach informs on whether provider leniency impacts the genetic signal captured in large scale genome-wide association studies of depression. Discussion These results will have implications for academics, clinicians and the more than 300 million individuals and their families suffering from depression worldwide.

• Qin, Qi; Ystrøm, Eivind; Eilertsen, Espen Moen; Ofstad, Sverre Berg; Ayorech, Ziada & Cheesman, Rosa Catherine Gillespie (2024). School-level Moderation of Multiple Within- Family Polygenic Index Effects on Educational Performance in MoBa (n=27476 Trios). Full text in Research Archive
• Sunde, Hans Fredrik; Eftedal, Nikolai Haahjem; Cheesman, Rosa Catherine Gillespie; Corfield, Elizabeth Claire; Kleppestø, Thomas Haarklau & Seierstad, Anne Caroline [Show all 9 contributors for this article] (2024). Genetic similarity between relatives provides evidence on the presence and history of assortative mating. Full text in Research Archive
• Yang, Tianfang; Ystrøm, Eivind; Valstad, Mathias; Eftedal, Nikolai Haahjem; Reichborn-Kjennerud, Ted & Krueger, Robert F [Show all 7 contributors for this article] (2024). The Intergenerational Impact of Borderline and Avoidant Personality Disorders on Child Academic Achievement: A Registry Study in Norway. Full text in Research Archive
• Eilertsen, Espen Moen; Eftedal, Nikolai Haahjem; Cheesman, Rosa Catherine Gillespie; Ayorech, Ziada; Ebeltoft, Joakim Coleman & Sunde, Hans Fredrik [Show all 9 contributors for this article] (2024). Multivariate parental effects across the internalizing-externalizing spectrum in childhood: results from the Norwegian Mother, Father, and Child Cohort Study. Full text in Research Archive
• Ystrøm, Eivind (2024). Maternal Perception of Big Five Personality Traits in Childhood and Self-reported Gender Fluidity in Adolescence: A Study from the Norwegian Mother, Father and Child Cohort (MoBa). Full text in Research Archive
• Czajkowski, Nikolai Olavi; Eftedal, Nikolai Haahjem; Yang, Tianfang; Valstad, Mathias; Reichborn-Kjennerud, Ted & Ystrøm, Eivind (2024). The Role of Parental Personality Disorders in High School Dropout: Insights from a Nationwide Cohort Study. Full text in Research Archive
• Valstad, Mathias; Eilertsen, Espen Moen; Timpe, Clara Marie Fides; Yang, Tianfang; Eftedal, Nikolai Haahjem & Reichborn-Kjennerud, Ted [Show all 8 contributors for this article] (2024). Genetic and environmental effects on diagnosed Borderline Personality Disorder (BPD) without clinic bias. Full text in Research Archive
• Ebeltoft, Joakim Coleman; Eilertsen, Espen Moen; Cheesman, Rosa Catherine Gillespie; Ayorech, Ziada; Hootegem, Arno Van & Lyngstad, Torkild Hovde [Show all 7 contributors for this article] (2024). Triangulating Approaches to Evaluate the Genetic and Environmental Composition of Socioeconomic Status. Full text in Research Archive
• Ystrøm, Eivind (2024). Childhood personality and adolescent performance in physical education: A sibling fixed-effects study. Full text in Research Archive
• Ystrøm, Eivind (2024). Studie: Personlighetene som klarer seg best på skolen. [Journal]. VG. Full text in Research Archive
• Porneso, Ralph Pascual Ortiz; Eilertsen, Espen Moen; Havdahl, Alexandra & Ystrøm, Eivind (2024). Non-additive genetic effects in academic performance. Full text in Research Archive
• Ystrøm, Eivind; Cheesman, Rosa Catherine Gillespie; Hootegem, Arno Van; Ghirardi, Gaia; Ofstad, Sverre Berg & Ebeltoft, Joakim Coleman (2024). Roads less traveled in social science genetics. Full text in Research Archive
• Ystrøm, Eivind (2024). Personlighet er et lotteri som påvirker hvordan vi gjør det på skolen. [Internet]. forskning.no. Full text in Research Archive
• Porneso, Ralph Pascual Ortiz; Eilertsen, Espen Moen; Havdahl, Alexandra & Ystrøm, Eivind (2024). Identifying genetic variants with non-additive and time-varying genetic effects using longitudinal data. Full text in Research Archive
• Ystrøm, Eivind; Eilertsen, Espen Moen; Cheesman, Rosa Catherine Gillespie; Ayorech, Ziada & Demange, Perline Aline Delle (2024). The dark matter of parenting – estimating the environmental importance of family members using genetics. Full text in Research Archive
• Ystrøm, Eivind (2024). Sammenhengen mellom symptomnivåer, genetisk risiko og skoleprestasjoner. Full text in Research Archive
• Cheesman, Rosa Catherine Gillespie; Anapaz, Ville; Alten, Sjoerd van; Abdellaoui, Abdel; Ebeltoft, Joakim Coleman & Porneso, Ralph Pascual Ortiz [Show all 16 contributors for this article] (2024). The Genetics of Educational Fields. Full text in Research Archive
• Peng, Qiyuan; Rietveld, Cornelius A.; Cheesman, Rosa Catherine Gillespie; Ystrøm, Eivind & Havdahl, Alexandra (2024). Causal Intergenerational Transmission of Education: How Do Parents Affect Children’s Educational Achievement? Full text in Research Archive
• Nes, Ragnhild Bang; Ayorech, Ziada; Mayerhofer, Lilian; Moffitt, Terrie; Ystrøm, Eivind & Caspi, Avshalom [Show all 7 contributors for this article] (2024). Surrounded by Genes: The Interplay of Core Family Genetic Profiles on Mothers’ Wellbeing Across 14 Years. Full text in Research Archive
• Ystrøm, Eivind (2024). Gene-Environment Interplay and Borderline Personality Disorder Symptoms Amid Stressful Life Events. Full text in Research Archive
• Peng, Qiyuan; Eilertsen, Espen Moen; Cheesman, Rosa Catherine Gillespie; Rietveld, Cornelius A.; Ystrøm, Eivind & Havdahl, Alexandra (2024). Parental Influence on Children's Educational Achievements: Analyzing Direct and Indirect Genetic Effects through Trio-GCTA. Full text in Research Archive
• Ebeltoft, Joakim Coleman; Eilertsen, Espen Moen; Cheesman, Rosa Catherine Gillespie; Ayorech, Ziada; Hootegem, Arno Van & Lyngstad, Torkild Hovde [Show all 7 contributors for this article] (2024). Parent SES and young people's mental health: Doctoral project. Full text in Research Archive
• Qin, Qi; Ystrøm, Eivind; Eilertsen, Espen Moen; Ofstad, Sverre Berg; Ayorech, Ziada & Cheesman, Rosa Catherine Gillespie (2024). School-level Moderation of Multiple Within- Family Polygenic Index Effects on Educational Performance in MoBa (n=27476 Trios). Full text in Research Archive
• Chegeni, Razieh; Nes, Ragnhild Bang; Cheesman, Rosa Catherine Gillespie; Ayorech, Ziada; Ystrøm, Eivind & Røysamb, Espen (2024). Surrounded by genes: Parental genetic effects on children’s mental health. Full text in Research Archive
• Valstad, Mathias; Eilertsen, Espen Moen; Cheesman, Rosa Catherine Gillespie; Ayorech, Ziada; Demange, Perline Aline Delle & Eftedal, Nikolai Haahjem [Show all 8 contributors for this article] (2024). Indirect genetic effects of siblings. Full text in Research Archive
• Chegeni, Razieh; Nes, Ragnhild Bang; Cheesman, Rosa Catherine Gillespie; Ayorech, Ziada; Ystrøm, Eivind & Røysamb, Espen (2024). Intergenerational transmission of internalizing behaviors: a multipolygenic score approach. Full text in Research Archive
• Demange, Perline Aline Delle; Eilertsen, Espen Moen & Ystrøm, Eivind (2024). Beyond trio: genetic effects in the extended family and proximal environments. Full text in Research Archive
• Peng, Qiyuan; Eilertsen, Espen Moen; Cheesman, Rosa Catherine Gillespie; Rietveld, Cornelius A.; Ystrøm, Eivind & Havdahl, Alexandra (2024). Parental Influence on Children's Educational Achievements: Analyzing Direct and Indirect Genetic Effects through Trio-GCTA. Full text in Research Archive
• Widding-Havnerås, Tarjei; Demange, Perline Aline Delle; Elwert, Felix; Borgen, Nicolai T.; Ystrøm, Eivind & Zachrisson, Henrik Daae (2024). Estimating Returns to Education Using Genetically Informed Designs. Full text in Research Archive
• Demange, Perline Aline Delle; Eilertsen, Espen Moen & Ystrøm, Eivind (2024). Beyond trio: genetic effects in the extended family and proximal environments. Full text in Research Archive
• Ofstad, Sverre Berg; Demange, Perline Aline Delle; Cheesman, Rosa Catherine Gillespie; Qin, Qi & Ystrøm, Eivind (2024). Nature Meets Schooling: Why Boys Fall Behind in GPA Despite Equal Genetic Potential (ESSGN). Full text in Research Archive
• Peng, Qiyuan; Eilertsen, Espen Moen; Cheesman, Rosa Catherine Gillespie; Rietveld, Cornelius A.; Ystrøm, Eivind & Havdahl, Alexandra (2024). Parental Influence on Children's Educational Achievements: Analyzing Direct and Indirect Genetic Effects through Trio-GCTA. Full text in Research Archive
• Yang, Tianfang; Ystrøm, Eivind; Valstad, Mathias; Eftedal, Nikolai Haahjem; Reichborn-Kjennerud, Ted & Czajkowski, Nikolai Olavi (2024). Parental Personality Disorder, Substance Abuse and Child Academic Performance: a Norwegian Registry Study. Full text in Research Archive
• Lund, Ingunn Olea; Hannigan, Laurie; Ask, Helga; Askelund, Jo Adrian Dahl; Hegemann, Laura & Corfield, Elizabeth Claire [Show all 12 contributors for this article] (2024). Triangulation in research. Full text in Research Archive
• Folstad, Siri Hausland; Edvoll, Maud; Røsand, Ingvild; Klomstén, Anne Torhild; Bjørnebekk, Gunnar & Røysamb, Espen [Show all 10 contributors for this article] (2024). Almost No Studies Worldwide Evaluate Effects of School Curriculum Reforms on Child Mental Health. Full text in Research Archive
• Folstad, Siri Hausland; Edvoll, Maud; Røsand, Ingvild; Klomstén, Anne Torhild; Bjørnebekk, Gunnar & Røysamb, Espen [Show all 10 contributors for this article] (2024). Rethinking Mental Health through Curriculum Reform: the Norwegian Model. Full text in Research Archive
• Porneso, Ralph Pascual Ortiz; Eilertsen, Espen Moen; Havdahl, Alexandra & Ystrøm, Eivind (2024). Non-additive genetic effects in academic performance. Full text in Research Archive
• Porneso, Ralph Pascual Ortiz; Eilertsen, Espen Moen; Havdahl, Alexandra & Ystrøm, Eivind (2024). Identifying genetic variants with non-additive and time-varying effects using longitudinal data. Full text in Research Archive
• Pettersen, Johanne Hagen; Eilertsen, Espen Moen; Hegemann, Laura; Hannigan, Laurie John; Lund, Ingunn Olea & Jensen, Pia [Show all 12 contributors for this article] (2024). Direct and indirect genetic inluences on mental distress in mother-father-offspring trios during the Covid-19 lockdown. Full text in Research Archive
• Ebeltoft, Joakim Coleman; Eilertsen, Espen Moen; Cheesman, Rosa Catherine Gillespie; Ayorech, Ziada; Hootegem, Arno Van & Lyngstad, Torkild Hovde [Show all 7 contributors for this article] (2024). Triangulating Approaches to Evaluate the Genetic and Environmental Composition of Socioeconomic Status: Multi-method study. Full text in Research Archive
• Ofstad, Sverre Berg; Demange, Perline Aline Delle; Cheesman, Rosa Catherine Gillespie; Qin, Qi & Ystrøm, Eivind (2024). Sex-specific gene x school interactions found by using within-family polygenic score and twin modelling. Full text in Research Archive
• Ofstad, Sverre Berg; Demange, Perline Aline Delle; Cheesman, Rosa Catherine Gillespie; Qin, Qi & Ystrøm, Eivind (2024). Nature Meets Schooling: Why Boys Fall Behind in GPA Despite Equal Genetic Potential. Full text in Research Archive
• Mayerhofer, Lilian Juliane Kozlowski; Nes, Ragnhild Bang; Yu, Baeksan; Ayorech, Ziada; Lan, Xiaoyu & Ystrøm, Eivind [Show all 7 contributors for this article] (2024). Journey of Love: Exploring Stability and Change in Relationship Satisfaction, Wellbeing, and Illbeing from Pregnancy to Three Years Postpartum. Full text in Research Archive
• Ebeltoft, Joakim Coleman; Eilertsen, Espen Moen; Cheesman, Rosa Catherine Gillespie; Ayorech, Ziada; Hootegem, Arno Van & Lyngstad, Torkild Hovde [Show all 7 contributors for this article] (2024). Genetic and environmental composition of SES. Full text in Research Archive
• Ebeltoft, Joakim Coleman; Eilertsen, Espen Moen; Cheesman, Rosa Catherine Gillespie; Ayorech, Ziada; Hootegem, Arno Van & Lyngstad, Torkild Hovde [Show all 7 contributors for this article] (2024). Doctoral project: Socioeconomic status and young people's mental health. Full text in Research Archive
• Mayerhofer, Lilian Juliane Kozlowski; Nes, Ragnhild Bang; Yu, Baeksan; Ayorech, Ziada; Lan, Xiaoyu & Ystrøm, Eivind [Show all 7 contributors for this article] (2024). Journey of Love: Exploring Stability and Change in Relationship Satisfaction, Wellbeing, and Illbeing from Pregnancy to Three Years Postpartum. Full text in Research Archive
• Ystrom, Eivind (2023). Depression afterer weaning can be a serious concern for some new moms. [Journal]. The Washington Post. doi: https:/www.washingtonpost.com/wellness/2023/10/19/postweaning-depression-anxiety-new-moms/. Full text in Research Archive
• Eftedal, Nikolai Haahjem; Eilertsen, Espen Moen; Sunde, Hans Fredrik; Kleppestø, Thomas Haarklau; Ystrøm, Eivind & Czajkowski, Nikolai Olavi (2023). Correlations on Norwegian national standardized tests between millions of pairs of relatives: Exploring the impacts of assortative mating and parental effects. Full text in Research Archive
• Ahmadzadeh, Yasmin I.; Eilertsen, Espen Moen; Cheesman, Rosa Catherine Gillespie; Ystrøm, Eivind & McAdams, Tom A. (2023). Are mothers’ prenatal emotional symptoms influenced by the foetal genome? Exploring the possibility of child-to- parent effects during pregnancy. Full text in Research Archive
• Sunde, Hans Fredrik; Eftedal, Nikolai Haahjem; Cheesman, Rosa Catherine Gillespie; Corfield, Elizabeth Claire; Kleppestø, Thomas Haarklau & Seierstad, Anne Caroline [Show all 9 contributors for this article] (2023). Genetic similarity between relatives provides evidence on the presence and history of assortative mating. Full text in Research Archive
• Cheesman, Rosa Catherine Gillespie; Eilertsen, Espen Moen & Ystrøm, Eivind (2023). School-level Moderation of Multiple Within- Family Polygenic Index Effects on Educational Performance in MoBa (n=27476 Trios). Full text in Research Archive
• Sunde, Hans Fredrik; Eftedal, Nikolai Haahjem; Cheesman, Rosa Catherine Gillespie; Corfield, Elizabeth Claire; Kleppestø, Thomas Haarklau & Seierstad, Anne Caroline [Show all 9 contributors for this article] (2023). Assortative mating strongly increases genetic similarity between distant relatives. Full text in Research Archive
• Maes, Hermine H.; Eftedal, Nikolai Haahjem; Eilertsen, Espen Moen & Ystrøm, Eivind (2023). Children of Relatives and Parents of Twins Modeling of BMI and Education in MoBa. Full text in Research Archive
• Sunde, Hans Fredrik; Eftedal, Nikolai Haahjem; Cheesman, Rosa Catherine Gillespie; Corfield, Elizabeth Claire; Kleppestø, Thomas Haarklau & Seierstad, Anne Caroline [Show all 9 contributors for this article] (2023). Assortative mating increases genetic similarity among distant relatives: evidence from polygenic scores. Full text in Research Archive
• Torvik, Fartein Ask; Sunde, Hans Fredrik; Cheesman, Rosa Catherine Gillespie; Eftedal, Nikolai Haahjem; Ystrøm, Eivind & Eilertsen, Espen Moen (2023). Within- and cross-trait assortative mating for educational attainment and mental and somatic health conditions: a total population study. Full text in Research Archive
• Bright, Joanna K.; Ahmadzadeh, Yasmin; Oginni, O.; Viding, Essi; Ystrøm, Eivind & McAdams, Tom A. (2023). A genetically informed investigation into the bidirectional links between parenting style and child externalizing behaviours. Full text in Research Archive
• Røysamb, Espen; Moffitt, Terrie; Caspi, Avshalom; Ystrøm, Eivind & Nes, Ragnhild Bang (2023). Worldwide wellbeing: Simulated twins reveal (missing) shared environments. Full text in Research Archive
• Ystrøm, Eivind (2023). Gener og prestasjon. [Radio]. NRK Dagsnytt 18. Full text in Research Archive Show summary

  Forsker mener betydningen av gener må vurderes bedre etter at ny studie viser at barn av foreldre med høy utdanning drar i fra de andre på skolen.

• Bjørnebekk, Astrid Kristine; Ystrøm, Eivind & Nordengen, Kaja (2023). Sitter personligheten din i hjernen? Full text in Research Archive
• Røysamb, Espen; Ystrøm, Eivind & Nes, Ragnhild Bang (2023). Wellbeing worldwide: Identifying the (missing) shared environment. Full text in Research Archive
• Askelund, Adrian Dahl; Hegemann, Laura; Corfield, Elizabeth Claire; Ystrøm, Eivind; Ask, Helga & Havdahl, Alexandra [Show all 7 contributors for this article] (2023). Genetic and environmental factors associated with differentiation between behavioural and emotional problems across early life. Full text in Research Archive
• Bright, Joanna K.; Ahmadzadeh, Yasmin; Viding, O.; Ystrøm, Eivind & McAdams, Thomas Andrew (2023). A genetically informed investigation into the bidirectional links between parenting style and child externalizing behaviours. Full text in Research Archive
• Mayerhofer, Lilian Juliane Kozlowski; Nes, Ragnhild Bang; Yu, Baeksan; Ayorech, Ziada; Lan, Xiaoyu & Ystrøm, Eivind [Show all 7 contributors for this article] (2023). From Romance to Motherhood: Transitions in Relationship Satisfaction, Wellbeing and Illbeing from Pregnancy to Toddlerhood. Full text in Research Archive
• Ebeltoft, Joakim Coleman; Eilertsen, Espen Moen; Cheesman, Rosa Catherine Gillespie; Ayorech, Ziada; Qin, Qi & Ystrøm, Eivind (2023). The inheritance of inequality: Comparing heritability estimates of socioeconomic status. Full text in Research Archive
• Mayerhofer, Lilian Juliane Kozlowski; Nes, Ragnhild Bang; Ayorech, Ziada; Bartels, Meike; Ystrøm, Eivind & Røysamb, Espen (2023). Early manifestations of genetic profile in mental health phenotypes and the role of maternal wellbeing: findings from MoBa and NTR. Full text in Research Archive
• Ayorech, Ziada; Cheesman, Rosa Catherine Gillespie; Eilertsen, Espen Moen; Havdahl, Alexandra & Ystrøm, Eivind (2023). Family-based approaches to gene-environment interplay. Full text in Research Archive
• Cheesman, Rosa Catherine Gillespie; Ystrom, Eivind; Ayorech, Ziada; Eilertsen, Espen Moen; Ystrøm, Eivind & Ayorech, Ziada (2023). The Anatomy of Educational Fields. Full text in Research Archive
• Cheesman, Rosa Catherine Gillespie; Ystrom, Eivind; Eilertsen, Espen Moen; Ayorech, Ziada & Ystrøm, Eivind (2023). The anatomy of educational fields. Full text in Research Archive
• Ayorech, Ziada; Davies, Neil; Smith, George Davey; Watson, Hunna J; Yilmaz, Zeynep & Bulik, Cynthia M [Show all 15 contributors for this article] (2023). Causal risk factors for childhood eating behaviours and adulthood anorexia nervosa. A between and within family Mendelian randomisation study. Full text in Research Archive
• Hannigan, Laurie J.; Lund, Ingunn Olea; Askelund, Jo Adrian Dahl; Ystrøm, Eivind; Corfield, Elizabeth Claire & Ask, Helga [Show all 7 contributors for this article] (2023). Genotype–environment interplay in associations between maternal drinking and offspring emotional and behavioral problems – CORRIGENDUM. Psychological Medicine. ISSN 0033-2917. doi: 10.1017/S0033291723003483. Full text in Research Archive
• Ayorech, Ziada; Cheesman, Rosa Catherine Gillespie; Eilertsen, Espen Moen; Havdahl, Alexandra & Ystrøm, Eivind (2023). The genetics of depression across the childbearing years. Full text in Research Archive
• Gjerde, Line Cecilie; Eilertsen, Espen Moen; McAdams, Tom A.; Cheesman, Rosa Catherine Gillespie; Moffitt, Terrie & Caspi, Avshalom [Show all 10 contributors for this article] (2023). Erratum: The p factor of psychopathology and personality in middle childhood: Genetic and gestational risk factors (Psychological Medicine (2023) DOI: 10.1017/S0033291723000077). Psychological Medicine. ISSN 0033-2917. doi: 10.1017/S0033291723000879. Full text in Research Archive
• Lund, Ingunn Olea; Hannigan, Laurie; Ask, Helga; Askelund, Jo Adrian Dahl; Hegemann, Laura & Corfield, Elizabeth Claire [Show all 11 contributors for this article] (2023). PRENATAL MATERNAL STRESS: TRIANGULATING EVIDENCE FOR INTRAUTERINE EXPOSURE EFFECTS ON BIRTH AND EARLY CHILDHOOD OUTCOMES ACROSS MULTIPLE APPROACHES. Full text in Research Archive
• Lund, Ingunn Olea; Hannigan, Laurie; Ask, Helga; Askelund, Jo Adrian Dahl; Hegemann, Laura & Corfield, Elizabeth Claire [Show all 11 contributors for this article] (2023). Prenatal maternal stress: triangulating evidence for intrauterine exposure effects on birth and early childhood outcomes across multiple approaches. Full text in Research Archive
• Maes, Hermine H.; Eftedal, Nikolai Haahjem; Eilertsen, Espen Moen & Ystrøm, Eivind (2023). Children of relatives and parents of twins modelling of BMI in MOBA. Full text in Research Archive
• Maes, Hermine H.; Eftedal, Nikolai Haahjem; Eilertsen, Espen Moen & Ystrøm, Eivind (2023). Children of relatives and parents of twins modelling of BMI and Education in MOBA. Full text in Research Archive
• Røysamb, Espen; Mayerhofer, Lilian Juliane Kozlowski; Hansen, Thomas; Ystrøm, Eivind & Yu, Baeksan (2023). Maternal wellbeing and illbeing from pregnancy to school age: A longitudinal study of co-development and interrelations. Full text in Research Archive
• Ayorech, Ziada; Torvik, Fartein Ask; Cheesman, Rosa Catherine Gillespie; Eilertsen, Espen Moen; Valstad, Mathias & Bjørndal, Ludvig Daae [Show all 9 contributors for this article] (2023). Leveraging family data can reveal the role of selection bias in genomic research. Full text in Research Archive
• Liu, Chaoyu; Ahmadzadeh, Yasmin I.; Baldwin, Jessie R.; Hannigan, Laurie John; Ystrøm, Eivind & McAdams, Tom A. (2023). Examining mechanisms underlying associations between exposure to antenatal maternal stressful life events and child mental health outcomes. Full text in Research Archive
• Qin, Qi; Cheesman, Rosa Catherine Gillespie; Eilertsen, Espen Moen; Ebeltoft, Joakim Coleman; Ayorech, Ziada & Ystrøm, Eivind (2023). School and geographical differences in the effect of heritable emotional and behavioral traits on educational performance. Full text in Research Archive
• Ystrøm, Eivind (2023). Getting within the between – gene-environment correlations and children without parents. Full text in Research Archive
• Qin, Qi; Cheesman, Rosa Catherine Gillespie; Eilertsen, Espen Moen; Ebeltoft, Joakim Coleman; Ayorech, Ziada & Ystrøm, Eivind (2023). School and geographical differences in the effect of heritable emotional and behavioural traits on educational performance. Full text in Research Archive
• Ystrøm, Eivind (2023). Schools in the interplay between genetic risk for high BMI and academic performance. Full text in Research Archive
• Ystrøm, Eivind (2023). Genes as environments – intergenerational transmission of mental health in the Norwegian Mother, Father and Child Cohort study. Full text in Research Archive
• Eilertsen, Espen Moen; Eftedal, Nikolai Haahjem; Cheesman, Rosa Catherine Gillespie; Ebeltoft, Joakim Coleman; Sunde, Hans Fredrik & Tandberg, Anneli Desire [Show all 8 contributors for this article] (2023). Multivariate parental effects across the internalizing-externalizing spectrum in childhood: results from the Norwegian Mother, Father, and Child Cohort Study. Full text in Research Archive
• Ebeltoft, Joakim Coleman; Eilertsen, Espen Moen; Cheesman, Rosa Catherine Gillespie; Ayorech, Ziada; Qin, Qi & Ystrøm, Eivind (2023). Inheritance of inequality: Comparing heritability estimates. Full text in Research Archive
• Ebeltoft, Joakim Coleman; Eilertsen, Espen Moen; Cheesman, Rosa Catherine Gillespie; Ayorech, Ziada; Qin, Qi & Ystrøm, Eivind (2023). Inheritance of inequality. Full text in Research Archive
• Askelund, Adrian Dahl; Hegemann, Laura; Corfield, Elizabeth Claire; Ask, Helga; Ystrøm, Eivind & Havdahl, Alexandra [Show all 7 contributors for this article] (2022). The genomics of psychiatric symptom differentiation in early life. Full text in Research Archive Show summary

  Background: An emerging body of evidence suggests that genetic risk for psychiatric conditions is diffuse, probabilistic in nature, and overlaps substantially across different domains. However, psychiatric conditions are diagnosed and treated as specific disorders based on differentiated symptom clusters. In the context of generalised genetic risk, it remains to be determined how distinct psychiatric conditions emerge. The prospects of using genomic data to predict individual-level risk for psychiatric conditions are at present unclear. For prediction to be useful, it needs to be both sensitive (identifying who is at risk) and specific (at risk for what). While increasing sample sizes for genetic discovery may boost sensitivity, the generalised nature of genetic risk implies that identifying predictors of differentiation of psychiatric symptoms may be needed to increase specificity. The Norwegian Mother, Father, and Child Cohort Study (MoBa) is a large population-based pregnancy cohort with genotype and phenotype data, ideally suited to address these questions. Methods: We used the Child Behavior Checklist to assess behavioural and emotional difficulties at ages 1.5, 3, and 5. Symptom¬ differentiation was operationalised as the relative level of these domains over time (behavioural difficulties – emotional difficulties = differentiation). This means that individuals with high scores have relatively more behavioural than emotional difficulties, and the inverse for low scores. These scores can be compared to overall difficulties (behavioural + emotional = total). Following a preregistered analysis plan, we estimated latent growth trajectories of differentiation across early childhood, as well as mediation effects of differentiation on symptoms of psychiatric conditions at age 8. We tested associations between 10 polygenic scores (PGS) for core neurodevelopmental and psychiatric conditions and the extent (intercept) and rate (slope) of the differentiation process. The analytic sample comprised 57,387 genotyped children (including 12,347 pairs of full siblings) from MoBa. We used multilevel structural equation models to account for unmeasured familial confounding, and corrected for multiple comparisons using FDR. Results: ADHD PGS predicted the extent and rate of differentiation toward behavioural difficulties in early childhood (βintercept = 0.10 [0.09, 0.11]; βslope = 0.02 [0.02, 0.03]), and the extent of differentiation at age 5 in turn mediated 33-37% of the PGS associations with ADHD symptoms at age 8. The ADHD PGS association was smaller for total difficulties (βintercept = 0.05 [0.04, 0.06]; βslope = 0.01 [0.01, 0.02]). Schizophrenia PGS predicted differentiation toward emotional difficulties at age 5 (βintercept = -0.03 [-0.04, -0.02]; βslope = -0.01 [-0.02, -0.01]), and bipolar disorder PGS predicted differentiation toward behavioural difficulties (βintercept = 0.02 [0.01, 0.03]; βslope = 0.01 [0.01, 0.02]) – though in both cases effect sizes were substantially smaller. Discussion: We identify genomic predictors of symptom differentiation in early life. Results support a direct effect of ADHD PGS on differentiation toward behavioural difficulties, independent of individuals’ total burden of symptoms. PGS for schizophrenia and bipolar disorder differentially associates with the development of emotional and behavioural difficulties in early childhood. This research may help refine risk predictions in child psychiatry, an important step to enable early prevention.

• Fabian, Streit; Witt, Stephanie H.; Hindley, Guy Frederick Lanyon; Kuja-Halkola, Ralf & Ystrøm, Eivind (2022). Genomics of borderline personality disorder. Full text in Research Archive Show summary

  Factors such as early trauma or abuse are well-established environmental risk factors for the development of Borderline Personality Disorder (BPD). Compared to other mental disorders, little attention has been paid to the contribution of genetic risk factors. The present symposium aims to give an overview of how family and twin studies, and molecular genetic studies can contribute to the understanding of the disorder, and its relationship to risk factors and comorbid disorders: Eivind Ystrom will present on how twin studies can be used to investigate genetic and environmental risk factors contributing to comorbidity between BPD, mental disorders, and substance abuse. Using interview data from a population-based twin study, Ystrom and colleagues have found that genetic factors are the main contributors to the 10-year stability of BPD. Genetic factors for BPD are to a great extent overlapping with the risk for antisocial PD and substance use disorders. However, BPD is related to stressful life events, internalizing symptoms and personality disorders, and substance abuse over and beyond what can be explained by common genetic risk factors. Ralf Kuja-Halkola will present how national health register data can be used to investigate genetic contributions. Using twins and siblings, familial aggregation of clinical BPD diagnosis was investigated, and the heritability of BPD was estimated to 46%. The familial co-aggregation between BPD and attention deficit hyperactivity disorder (ADHD) was estimated, e.g. full siblings of individuals with ADHD diagnosis have a 2.8 times increased risk of having a BPD diagnosis compared to full siblings of individuals without ADHD diagnosis. Additionally, the co-aggregation in full siblings between BPD and a range of psychiatric and somatic disorders, and behavioral traits will be presented. Fabian Streit will present the initial results of the largest genome-wide association study (GWAS) which systematically investigates the contribution of common genetic variants to BPD. In a meta-analysis including over 6000 cases, and 500,000 controls. The results highlight first associated genes, also related to comorbid disorders, such as post-traumatic stress disorder (PTSD), or ADHD. Polygenic risk scores predicted up to 3% of the variance in case-control status. Positive genetic correlations were observed with other psychiatric disorders, most pronounced with PTSD, depression, ADHD, and anxiety. Additional analyses indicated genetic correlations with factors such as somatic disorders, pain, mood swings, childhood maltreatment, and material deprivation. Guy Hindley will present molecular genetic investigations of mood instability, a key component of BPD. A recent GWAS identified a strong positive genetic correlation of the trait with depression but weak correlations with bipolar disorder and schizophrenia. However, genetic correlation does not capture shared genetic variants with mixed effect directions. By applying statistical tools which capture mixed effect directions, the extensive genetic overlap between mood instability and all three mental disorders could be demonstrated, irrespective of their genetic correlation. This overlap was used to identify 246 novel genetic loci associated with mood instability. Biological characterization highlighted a convergence on synaptic gene-sets. These findings indicate shared neurobiological mechanisms between mood instability and diverse mental disorders.

• Ystrøm, Eivind & Reichborn-Kjennerud, Ted (2022). Genomics of borderline personality disorder: Common Genetic Factors for Personality Disorders, Common Mental Disorders, Substance Abuse, and Stressful Life Events: A population based longitudinal twin study. Full text in Research Archive Show summary

  Objectives: To evaluate the contribution of genetic and environmental factors for stability in, comorbidity with, and life events related to personality disorders. Methods: DSM-IV criteria for 10 personality disorders were assessed using structured interviews in 2801 Norwegian twins in early adulthood (age 28; range 19-36) and again in 2282 twins 10 years later. Biometric models were used on criteria counts to analyze the genetic and environmental factors for PDs and: 10-year stability, comorbidity with common mental disorders and psychotic-like experiences, substance abuse, and stressful life events. Results: Heritability of PDs were estimated to be 40% to 20% heritable. The 10-year stability estimated as tetrachoric correlation of PDs ranged from .35 to .58. Genetic variants influencing PDs were estimated to be the same over 10 years, the environmental factors were estimated to change 74-84% over the same period. Genetic and environmental factors for comorbidity between PDs and common mental disorders have different dimensionality and structure. The link between PDs and substance use are dependent on the specific criteria endorsed rather than at the disorder level. Stressful life events are important for the development of PDs and substance use over and beyond what can be explained by life-course selection due to genetic risk. Conclusion: Although PDs at specific assessments are mostly influenced by environmental factors, genetic factors are more important in explaining stability and comorbidity. The unequal structure of genetic and environmental factors leads to a mismatch between the observed comorbidity between PDs and mental disorders and the expected commonality in genetic factors. Aggregation of symptoms and disorders according to the estimated genetic structure could improve the precision of molecular genetic studies. This longitudinal twin study has also shown that PDs are related to stressful life events, mental disorders, and substance abuse over and beyond what can be explained by genetic risk.

• Folstad, Siri Hausland; Edvoll, Maud; Røsand, Ingvild; Ystrøm, Eivind; Klomsten, Anne Torhild & Nes, Ragnhild Bang [Show all 9 contributors for this article] (2022). Child Mental Health Effects of Large-Scale School Curricular Changes: A Systematic Review. Full text in Research Archive
• Bjørndal, Ludvig Daae; Eilertsen, Espen Moen; Baldwin, Jessie R.; Ayorech, Ziada; Cheesman, Rosa Catherine Gillespie & Ahmadzadeh, Yasmin [Show all 13 contributors for this article] (2022). Disentangling intrafamilial effects on maternal depression using trio-GCTA. Full text in Research Archive
• Ystrøm, Eivind & Eia, Harald (2022). PharmaTox-video med Eivind Ystrøm og Harald Eia. Full text in Research Archive
• Ayorech, Ziada; Cheesman, Rosa Catherine Gillespie; Eilertsen, Espen Moen; Torvik, Fartein Ask; Andreassen, Ole & Havdahl, Alexandra Karoline Saasen [Show all 7 contributors for this article] (2022). The genetics of depression across the childbearing years. Full text in Research Archive
• Hannigan, Laurie John; Lund, Ingunn Olea; Askelund, Adrian Dahl; Ystrøm, Eivind; Corfield, Elizabeth Claire & Ask, Helga [Show all 7 contributors for this article] (2022). Gene-environment interplay in associations between maternal at-risk drinking and early childhood emotional and behavioural development in the Norwegian Mother, Father, and Child Cohort. Full text in Research Archive
• Demange, Perline; Eilertsen, Espen Moen; Nordmo, Magnus; Torvik, Fartein Ask; Lyngstad, Torkild Hovde & Nivard, Michel [Show all 8 contributors for this article] (2022). Genetic and pedigree designs to investigate the effects of parental psychopathology on children's school performance. Full text in Research Archive
• Ahmadzadeh, Yasmin; Eilertsen, Espen Moen; Wechsler, Daniel; Cheesman, Rosa Catherine Gillespie; Ayorech, Ziada & Rayner, Cristopher [Show all 8 contributors for this article] (2022). Are mothers' prenatal emotional symptoms influenced by the foetal genome? Exploring the possibility of child-to-parent effects during pregnancy. Full text in Research Archive
• Eilertsen, Espen Moen; Cheesman, Rosa Catherine Gillespie; Ayorech, Ziada; Røysamb, Espen; Pingault, Jean-Baptiste & Njølstad, Pål Rasmus [Show all 11 contributors for this article] (2022). A trio-gcta study of indirect and direct genetic effects on hyperactivity, inattention, conduct problems, and oppositional-defiant behaviors. Full text in Research Archive
• Ystrøm, Eivind (2022). Er det egentlig bra for hjertet med litt alkohol? [Journal]. Nettavisen. Full text in Research Archive
• Ystrøm, Eivind & Tesli, Martin Steen (2022). Personlighetstrekket som gir angst. [Journal]. Dagbladet. Full text in Research Archive
• Eilertsen, Espen Moen & Ystrøm, Eivind (2022). Multilevel models in genetics. Full text in Research Archive
• Ystrøm, Eivind (2022). Bruk av data fra Statistisk sentralbyrå. Full text in Research Archive
• Ystrøm, Eivind & Spilde, Ingrid (2022). Alkohol hindrer ikke hjertesykdom. [Internet]. forskning.no. Full text in Research Archive
• Ystrøm, Eivind (2022). PharmaTox-video med Eivind Ystrøm og Harald Eia. [Internet]. uio.no. Full text in Research Archive
• Mayerhofer, Lilian Juliane Kozlowski; Nes, Ragnhild Bang; Lan, Xiaoyu; Czajkowski, Nikolai Olavi; Ystrøm, Eivind & Røysamb, Espen (2022). Social support and wellbeing across the pre- and postnatal period in women victim of abuse: Findings from the Norwegian Mother, Father and Child Cohort Study. Full text in Research Archive
• Bjørndal, Ludvig Daae; Eilertsen, Espen Moen; Baldwin, Jessie R.; Ayorech, Ziada; Cheesman, Rosa Catherine Gillespie & Ahmadzadeh, Yasmin [Show all 13 contributors for this article] (2022). Disentangling intrafamilial effects on maternal depression using trio-GCTA. European Neuropsychopharmacology. ISSN 0924-977X. 63. doi: 10.1016/j.euroneuro.2022.07.125. Full text in Research Archive
• Ahmadzadeh, Yasmin & Ystrøm, Eivind (2022). Mental health in families: one genomic and one qualitative study. Full text in Research Archive
• Eilertsen, Espen Moen; Cheesman, Rosa Catherine Gillespie; Ayorech, Ziada; Røysamb, Espen; Pingault, Jean-Baptiste & Njølstad, Pål Rasmus [Show all 11 contributors for this article] (2022). A trio-gcta study of indirect and direct genetic effects on hyperactivity, inattention, conduct problems, and oppositional-defiant behaviors. European Neuropsychopharmacology. ISSN 0924-977X. 63. doi: 10.1016/j.euroneuro.2022.07.307. Full text in Research Archive
• Ahmadzadeh, Yasmin; Eilertsen, Espen Moen; Wechsler, Daniel; Cheesman, Rosa Catherine Gillespie; Ayorech, Ziada & Rayner, Cristopher [Show all 8 contributors for this article] (2022). Are mothers' prenatal emotional symptoms influenced by the foetal genome? Exploring the possibility of child-to-parent effects during pregnancy. European Neuropsychopharmacology. ISSN 0924-977X. doi: 10.1016/j.euroneuro.2022.07.346. Full text in Research Archive
• Nygaard, Egil; Ystrøm, Eivind; Nes, Ragnhild Bang; Røysamb, Espen; Klomsten, Anne Torhild & Bjørnebekk, Gunnar [Show all 8 contributors for this article] (2022). Effekt av det tverrfaglige temaet Folkehelse og livsmestring. Full text in Research Archive
• Barkhuizen, Wikus; Pingault, Jean-Baptiste; Wang, Biyao; Hannigan, Laurie John; Eilertsen, Espen Moen & Andreassen, Ole [Show all 14 contributors for this article] (2021). Direct and indirect genetic influences involved in the intergenerational transmission of risk for ADHD in the Norwegian Mother, Father and Child Cohort. Full text in Research Archive
• Badini, Isabella; Lyngstad, Torkild Hovde; Eilertsen, Espen Moen; Ahmadzadeh, Yasmin I.; Wechsler, Daniel L & Zachrisson, Henrik Daae [Show all 10 contributors for this article] (2021). Socioeconomic status and risk for child emotional and behavioral problems: Exploring gene-environment interaction in the presence of gene-environment correlation using extended families in the Norwegian Mother, Father and Child Birth Cohort Study. Full text in Research Archive
• Bjørndal, Ludvig Daae & Ystrøm, Eivind (2021). Stressful life events increase risk of depression: A population-based twin study. Full text in Research Archive
• Wechsler, Daniel L; Rijsdijk, Fruhling; Eilertsen, Espen Moen; Ystrøm, Eivind; Ahmadzadeh, Yasmin I. & Badini, Isabella [Show all 8 contributors for this article] (2021). Do adult ADHD symptoms share genetic underpinnings with child ADHD symptoms and those of related comorbid childhood disorders? Comparing within-child and mother-child genetic correlations in a large Norwegian Children-of-Twins-and- Siblings cohort. Full text in Research Archive
• Ayorech, Ziada; Cheesman, Rosa Catherine Gillespie; Eilertsen, Espen Moen; Havdahl, Alexandra & Ystrøm, Eivind (2021). Polygenic P: Characterising the role of general liability to psychopathology in maternal depression. Full text in Research Archive
• Nordeng, Hedvig Marie Egeland & Ystrøm, Eivind (2021). Forskere: – Har kostet mange gravide og barselkvinner dyrt. VG : Verdens gang. ISSN 0805-5203. Full text in Research Archive
• Arneberg, Vilde Sofie; Fodstad, Vilde & Ystrøm, Eivind (2021). Stressful Life Events and Borderline Personality Disorder Traits. Full text in Research Archive
• Nygaard, Egil; Nes, Ragnhild Bang; Ystrøm, Eivind; Klomsten, Anne Torhild; Bjørnebekk, Gunnar & Folstad, Siri Hausland [Show all 7 contributors for this article] (2021). Evaluering av implementering av det tverrfaglige temaet «Folkehelse og livsmestring» i norske skoler. Full text in Research Archive
• Ayorech, Ziada; Cheesman, Rosa Catherine Gillespie; Eilertsen, Espen Moen; Torvik, Fartein Ask; Andreassen, Ole & Havdahl, Alexandra [Show all 7 contributors for this article] (2021). Investigating Heterogeneity in Depression Using Multiple Polygenic Scores. Full text in Research Archive
• Nygaard, Egil; Ystrøm, Eivind; Nes, Ragnhild Bang; Røysamb, Espen; Klomsten, Anne Torhild & Bjørnebekk, Gunnar [Show all 7 contributors for this article] (2021). Effekt av det tverrfaglige temaet Folkehelse og livsmestring. Full text in Research Archive
• Ystrøm, Eivind (2021). The role of genetics in health inequality research. Full text in Research Archive
• Kleppestø, Thomas Haarklau; Eilertsen, Espen Moen; Bergen, Elsje van; Zeitsch, Brendan; Sunde, Hans Fredrik & Nordmo, Magnus [Show all 10 contributors for this article] (2021). Intergenerational Transmission of ADHD: More Evidence for Heritability than Fast Life History. Behavior Genetics. ISSN 0001-8244. 51(6), p. 717–717. Full text in Research Archive
• Kleppestø, Thomas Haarklau; Eilertsen, Espen Moen; Bergen, Elsje van; Zeitsch, Brendan; Sunde, Hans Fredrik & Nordmo, Magnus [Show all 10 contributors for this article] (2021). Intergenerational Transmission of ADHD: More Evidence for Heritability than Fast Life History. Full text in Research Archive
• Ayorech, Ziada; Cheesman, Rosa Catherine Gillespie; Eilertsen, Espen Moen; Torvik, Fartein Ask; Andreassen, Ole & Havdahl, Alexandra [Show all 7 contributors for this article] (2021). Investigating Heterogeneity in Depression Using Multiple Polygenic Scores. European Neuropsychopharmacology. ISSN 0924-977X. 51, p. E161–E161. Full text in Research Archive
• Ystrøm, Eivind (2021). Growth mixture modelling/group based trajectory modelling. Full text in Research Archive
• Ayorech, Ziada; Cheesman, Rosa Catherine Gillespie; Eilertsen, Espen Moen; Havdahl, Alexandra & Ystrøm, Eivind (2021). Polygenic P: Characterising the role of general liability to psychopathology in maternal depression. Behavior Genetics. ISSN 0001-8244. 51(5), p. 690–690. Full text in Research Archive
• Wechsler, Daniel L; Rijsdijk, Fruhling; Eilertsen, Espen Moen; Ystrøm, Eivind; Ahmadzadeh, Yasmin I. & Badini, Isabella [Show all 8 contributors for this article] (2021). Do adult ADHD symptoms share genetic underpinnings with child ADHD symptoms and those of related comorbid childhood disorders? Comparing within-child and mother-child genetic correlations in a large Norwegian Children-of-Twins-and- Siblings cohort. Behavior Genetics. ISSN 0001-8244. 51(6), p. 755–755. Full text in Research Archive
• Bjørndal, Ludvig Daae & Ystrøm, Eivind (2021). Stressful life events increase risk of depression: A population-based twin study. Behavior Genetics. ISSN 0001-8244. 51(6), p. 696–696. doi: 10.1007/s10519-021-10087-3. Full text in Research Archive
• Barkhuizen, Wikus; Pingault, Jean-Baptiste; Wang, Biyao; Hannigan, Laurie John; Eilertsen, Espen Moen & Andreassen, Ole [Show all 14 contributors for this article] (2021). Direct and indirect genetic influences involved in the intergenerational transmission of risk for ADHD in the Norwegian Mother, Father and Child Cohort. Behavior Genetics. ISSN 0001-8244. 51(6), p. 692–691. Full text in Research Archive
• Badini, Isabella; Lyngstad, Torkild Hovde; Eilertsen, Espen Moen; Ahmadzadeh, Yasmin I.; Wechsler, Daniel L & Zachrisson, Henrik Daae [Show all 10 contributors for this article] (2021). Socioeconomic status and risk for child emotional and behavioral problems: Exploring gene-environment interaction in the presence of gene-environment correlation using extended families in the Norwegian Mother, Father and Child Birth Cohort Study. Behavior Genetics. ISSN 0001-8244. 51(6), p. 691–691. Full text in Research Archive
• Middeldorp, Christel M.; Jami, Eshim; Sallis, Hannah; Ystrøm, Eivind; Pingault, Jean-Baptiste & Munafo, M [Show all 7 contributors for this article] (2021). The Role of Genetic Nurturing Effects in Childhood Psychopathology. Full text in Research Archive
• Ystrøm, Eivind (2021). Twin studies with unknown zygosity. Full text in Research Archive
• Middeldorp, Christel M.; Jami, Eshim; Sallis, Hannah; Ystrøm, Eivind; Pingault, Jean-Baptiste & Munafo, M [Show all 7 contributors for this article] (2021). The Role of Genetic Nurturing Effects in Childhood Psychopathology. European Neuropsychopharmacology. ISSN 0924-977X. 51, p. e177–e177. Full text in Research Archive
• Ystrøm, Eivind (2021). #09 Arvelig miljø? Full text in Research Archive
• Arneberg, Vilde Sofie; Fodstad, Vilde & Ystrøm, Eivind (2021). Stressful Life Events and Borderline Personality Disorder Traits. Behavior Genetics. ISSN 0001-8244. 51(5), p. 690–690. Full text in Research Archive
• Ystrøm, Eivind (2020). Ett personlighetstrekk avgjør risiko for psykisk sykdom. [Journal]. Nettavisen. Full text in Research Archive
• Borgen, Nicolai T.; Hermansen, Are Skeie; Lyngstad, Torkild Hovde & Ystrøm, Eivind (2020). Misvisende om utdanningsulikhet. Aftenposten (morgenutg. : trykt utg.). ISSN 0804-3116. Full text in Research Archive
• Torvik, Fartein Ask; Eilertsen, Espen Moen; Hannigan, Laurie John; Havdahl, Alexandra & Ystrøm, Eivind (2020). Assortative mating and the usefulness of polygenic scores in extended pedigrees. Full text in Research Archive
• Cheesman, Rosa Catherine Gillespie; McAdams, Tom A. & Ystrøm, Eivind (2020). How important are parents in the development of child anxiety and depression? A genomic analysis of parent-offspring trios in the Norwegian Mother Father and Child Cohort Study. Full text in Research Archive
• Ahmadzadeh, Yasmin; McAdams, Tom & Ystrøm, Eivind (2020). Familial risk for internalising: using children-of-twins designs to examine genetic transmission and parent-child interactions. Full text in Research Archive
• Cheesman, Rosa Catherine Gillespie; McAdams, Tom A. & Ystrøm, Eivind (2020). How important are parents in the development of child anxiety and depression. Full text in Research Archive
• Cheesman, Rosa Catherine Gillespie; McAdams, Tom A. & Ystrøm, Eivind (2020). How important are parents in the development of child anxiety and depression? Full text in Research Archive
• Cheesman, Rosa Catherine Gillespie; McAdams, Tom A. & Ystrøm, Eivind (2020). How important are parents in the development of child anxiety and depression? Full text in Research Archive
• Cheesman, Rosa Catherine Gillespie; McAdams, Tom A. & Ystrøm, Eivind (2020). Family-based genomics and gene-environment interplay. Full text in Research Archive
• Cheesman, Rosa Catherine Gillespie & Ystrøm, Eivind (2020). Decoding genetic nurture effects on education. Full text in Research Archive
• Ystrøm, Eivind (2020). Novel genetic methods. Full text in Research Archive
• Ystrøm, Eivind (2020). Hvor viktig er nabolaget for barns psykiske helse? Full text in Research Archive
• Wood, Mollie; Cohen, Jacqueline Mallory; Ystrøm, Eivind; Nordeng, Hedvig Marie Egeland & Hernandez-Diaz, Sonia (2020). Response to: Modelling paternal exposure as a negative control. International Journal of Epidemiology. ISSN 0300-5771. 49(3), p. 1054–1055. doi: 10.1093/ije/dyaa055. Full text in Research Archive
• Ystrøm, Eivind (2019). Nesten all psykisk sykdom har ett personlighetstrekk til felles. [Journal]. KK. Full text in Research Archive
• Ystrøm, Eivind (2019). Her og Nå - Er litt alkohol tidlig i svangerskapet skadelig? [Radio]. NRK Radio. Full text in Research Archive
• Ystrøm, Eivind (2019). Slik overføres risiko for misbruk mellom generasjoner. [Journal]. Rus & Samfunn. Full text in Research Archive
• Cheesman, Rosa Catherine Gillespie; Eilertsen, Espen Moen; Ahmadzadeh, Yasmin; Gjerde, Line C.; Hannigan, Laurie & Havdahl, Alexandra [Show all 9 contributors for this article] (2019). Separating child and parent influences on child depression and anxiety using genomic family data. Full text in Research Archive
• Middeldorp, CM; Akingbuwa, O; Jarvelin, MR; Lichtenstein, Paul; Lundstrom, S & Kuja-Halkola, Ralf [Show all 13 contributors for this article] (2019). The value of polygenic risk scores in predicting the transition from childhood and adolescent psychiatric symptoms into chronic adult psychopathology. European Neuropsychopharmacology. ISSN 0924-977X. 29, p. 1314–1314. doi: 10.1016/j.euroneuro.2018.08.455. Full text in Research Archive
• Ystrøm, Eivind (2019). Genforskerens etiske dilemmaer. [Journal]. Tidsskrift for Norsk psykologforening. Full text in Research Archive
• Jami, Eshim; Eilertsen, Espen Moen; Hammerschlag, Anke R.; Sallis, H; Qiao, Z & Evans, David [Show all 9 contributors for this article] (2019). Maternal and Paternal Effects on Offspring Internalizing Problems: Findings from Family Data and Extended GCTA Analysis. European Neuropsychopharmacology. ISSN 0924-977X. 29, p. S16–S17. doi: 10.1016/j.euroneuro.2019.07.034. Full text in Research Archive
• Middeldorp, CM; Akingbuwa, O; Jarvelin, MR; Lichtenstein, Paul; Lundstrom, S & Munafo, M [Show all 13 contributors for this article] (2019). Do shared genetic factors explain the prediction of bipolar disorder by childhood psychiatric symptoms? Full text in Research Archive
• Cheesman, Rosa Catherine Gillespie; Eilertsen, Espen Moen; Ahmadzadeh, Yasmin; Gjerde, Line C.; Hannigan, Laurie & Havdahl, Alexandra [Show all 9 contributors for this article] (2019). Separating child and parent influences on child depression and anxiety using genomic family data. European Neuropsychopharmacology. ISSN 0924-977X. 29, p. S119–S119. doi: 10.1016/j.euroneuro.2019.08.012. Full text in Research Archive
• Ystrøm, Eivind & Eilertsen, Espen Moen (2019). Deconstructing the history of genotype-phenotype associations in humans. Science. ISSN 0036-8075. 365(6460). Full text in Research Archive
• Middeldorp, CM; Akingbuwa, O; Jarvelin, MR; Lichtenstein, Paul; Lundstrom, S & Kuja-Halkola, Ralf [Show all 13 contributors for this article] (2019). The value of polygenic risk scores in predicting the transition from childhood and adolescent psychiatric symptoms into chronic adult psychopathology. Full text in Research Archive
• Middeldorp, CM; Akingbuwa, O; Jarvelin, MR; Lichtenstein, Paul; Lundstrom, S & Munafo, M [Show all 13 contributors for this article] (2019). Do shared genetic factors explain the prediction of bipolar disorder by childhood psychiatric symptoms? Bipolar Disorders. ISSN 1398-5647. 21, p. 18–18. Full text in Research Archive
• Jami, Eshim; Eilertsen, Espen Moen; Hammerschlag, Anke R.; Sallis, H; Qiao, Z & Evans, David [Show all 9 contributors for this article] (2019). Maternal and Paternal Effects on Offspring Internalizing Problems: Findings from Family Data and Extended GCTA Analysis. Full text in Research Archive
• Ystrøm, Eivind (2019). Intergenerational transmission of risk and mobility: genes, households, and neighborhoods. Full text in Research Archive
• Ystrøm, Eivind (2019). Genetics of neurodevelopmental disorders. Full text in Research Archive
• Ask, Helga; Eilertsen, Espen Moen; Gjerde, Line C.; Gustavson, Kristin; Hannigan, Laurie John & Havdahl, Alexandra [Show all 11 contributors for this article] (2019). Intergenerational transmission of parental neuroticism to offspring neuroticism, depression, and anxiety. Full text in Research Archive
• Gjerde, Line C.; Eilertsen, Espen Moen; Hannigan, Laurie; Eley, T.C.; Røysamb, Espen & Reichborn-Kjennerud, Ted [Show all 9 contributors for this article] (2019). To what extent can passive genetic transmission account for associations between maternal depressive symptoms and child early life psychopathology symptoms? Full text in Research Archive
• Ahmadzadeh, Yasmin; Ystrøm, Eivind & McAdams, Tom A. (2019). Exploring associations between maternal internalising and offspring adjustment, using genetically sensitive research designs. Full text in Research Archive
• Ahmadzadeh, Yasmin; Eilertsen, Espen Moen; Hannigan, Laurie; Gjerde, Line C.; Cheesman, Rosa Catherine Gillespie & Ystrøm, Eivind [Show all 7 contributors for this article] (2019). Intergenerational Associations between Maternal Internalising and Offspring Temperament During Early Childhood. Full text in Research Archive
• Ahmadzadeh, Yasmin; Ystrøm, Eivind & McAdams, Tom A. (2019). Associations between maternal internalising and offspring temperament: Investigating both genetic and environmental intergenerational effects. Full text in Research Archive
• Cheesman, Rosa Catherine Gillespie; Ystrøm, Eivind & McAdams, Tom A. (2019). How important are parents in the development of child anxiety and depression? A genomic analysis of parent-offspring trios in the Norwegian Mother and Child Birth Cohort Study. Full text in Research Archive
• McAdams, Tom A.; Ahmadzadeh, Yasmin; Ystrøm, Eivind & Torvik, Fartein Ask (2019). The Role of Parents in the Development of Emotional and Behavioural Problems in Their Children: Genetically Informative Approaches from Conception through Childhood. Full text in Research Archive
• McAdams, Tom A.; Ahmadzadeh, Yasmin; Torvik, Fartein Ask & Ystrøm, Eivind (2019). Stress During Pregnancy: Potential Effects on Child Development. Full text in Research Archive
• Ystrøm, Eivind (2019). Do Child and Adult ADHD Have the Same Genetic Risk Factors? Full text in Research Archive
• Cheesman, Rosa Catherine Gillespie; Eilertsen, Espen Moen; Ahmadzadeh, Yasmin; Gjerde, Line C.; Hannigan, Laurie & Havdahl, Alexandra [Show all 9 contributors for this article] (2019). Separating child and parent influences on child emotional problems using genomic family data. Full text in Research Archive
• Torvik, Fartein Ask; Eilertsen, Espen Moen; Ask, Helga; Gustavson, Kristin; McAdams, Tom A. & Ystrøm, Eivind (2019). Mechanisms linking parental education with symptoms of ADHD and depression in children. Full text in Research Archive
• Eftedal, Nikolai Haahjem; Kleppestø, Thomas Haarklau; Røysamb, Espen; Vassend, Olav; Ystrøm, Eivind & Thomsen, Lotte (2019). Moral opportunism: A unique genetic grounding associates lesser guilt from perpetrating injustice with greater sensitivity to being the victim of it. Full text in Research Archive
• Hur, Yoon-Mi; Bogl, Leonie H.; Ordonana, Juan R.; Taylor, Jeanette; Hart, Sara A. & Tuvblad, Catherine [Show all 10 contributors for this article] (2019). Twin family registries worldwide: An important resource for scientific research. Twin Research and Human Genetics. ISSN 1832-4274. p. 1–11. doi: 10.1017/thg.2019.121. Full text in Research Archive
• Burdzovic, Jasmina; Torvik, Fartein Ask; Ystrøm, Eivind; Skurtveit, Svetlana; Handal, Marte & Lund, Ingunn Olea (2019). Alcohol use disorder (AUD) in offspring following exposure to parental risk constellations during adolescence: A combined HUNT survey and health registries study. Full text in Research Archive
• Lupattelli, Angela; Mahic, Milada; Handal, Marte; Ystrøm, Eivind; Reichborn-Kjennerud, Ted & Nordeng, Hedvig Marie Egeland (2019). Risk of attention deficit hyperactivity disorder in childhood after exposure to serotonergic antidepressants in pregnancy. Pharmacoepidemiology and Drug Safety. ISSN 1053-8569. Full text in Research Archive
• Lund, Ingunn Olea; Skurtveit, Svetlana; Handal, Marte; Bukten, Anne; Torvik, Fartein Ask & Ystrøm, Eivind [Show all 7 contributors for this article] (2019). Association of Constellations of Parental Risk With Children's Subsequent Anxiety and Depression: Findings From a HUNT Survey and Health Registry Study. Full text in Research Archive
• Gustavson, Kristin; Torvik, Fartein Ask; Gjerde, Line C.; Ask, Helga; McAdams, Tom & Reichborn-Kjennerud, Ted [Show all 8 contributors for this article] (2019). Genetic and environmental contributions to comorbidity between ADHD and emotional problems in school aged children. Full text in Research Archive
• Gustavson, Kristin; Torvik, Fartein Ask; Gjerde, Line C.; Ask, Helga; McAdams, Tom & Reichborn-Kjennerud, Ted [Show all 8 contributors for this article] (2019). Genetic and environmental contributions to comorbidity between ADHD and emotional problems in school aged children. Behavior Genetics. ISSN 0001-8244. 49(6), p. 544–544. doi: 10.1007/s10519-019-09973-8. Full text in Research Archive
• Cheesman, Rosa Catherine Gillespie; Eilertsen, Espen Moen; Ahmadzadeh, Yasmin; Gjerde, Line C.; Hannigan, Laurie & Havdahl, Alexandra [Show all 9 contributors for this article] (2019). Separating child and parent influences on child emotional problems using genomic family data. Behavior Genetics. ISSN 0001-8244. 49(6), p. 523–524. doi: 10.1007/s10519-019-09973-8. Full text in Research Archive
• Ahmadzadeh, Yasmin; Eilertsen, Espen Moen; Hannigan, Laurie; Gjerde, Line C.; Cheesman, Rosa Catherine Gillespie & Ystrøm, Eivind [Show all 7 contributors for this article] (2019). Intergenerational Associations between Maternal Internalising and Offspring Temperament During Early Childhood. Behavior Genetics. ISSN 0001-8244. 49(6), p. 503–503. doi: 10.1007/s10519-019-09973-8. Full text in Research Archive
• Ask, Helga; Eilertsen, Espen Moen; Gjerde, Line C.; Gustavson, Kristin; Hannigan, Laurie John & Havdahl, Alexandra [Show all 11 contributors for this article] (2019). Intergenerational transmission of parental neuroticism to offspring neuroticism, depression, and anxiety. Behavior Genetics. ISSN 0001-8244. 49(6), p. 548–548. doi: 10.1007/s10519-019-09973-8. Full text in Research Archive
• Gjerde, Line C.; Eilertsen, Espen Moen; Hannigan, Laurie; Eley, T.C.; Røysamb, Espen & Reichborn-Kjennerud, Ted [Show all 9 contributors for this article] (2019). To what extent can passive genetic transmission account for associations between maternal depressive symptoms and child early life psychopathology symptoms? Behavior Genetics. ISSN 0001-8244. 49(6), p. 520–520. doi: 10.1007/s10519-019-09973-8. Full text in Research Archive
• McAdams, Tom; Hannigan, Laurie; Eilertsen, Espen Moen; Gjerde, Line C. & Ystrøm, Eivind (2019). Does Maternal Stress During Pregnancy Predict Child Emotional and Behavioural Problems? Accounting for rGE and Exploring GxE. Behavior Genetics. ISSN 0001-8244. 49(6), p. 506–506. doi: 10.1007/s10519-019-09973-8. Full text in Research Archive
• McAdams, Tom; Hannigan, Laurie; Eilertsen, Espen Moen; Gjerde, Line C. & Ystrøm, Eivind (2019). Does Maternal Stress During Pregnancy Predict Child Emotional and Behavioural Problems? Accounting for rGE and Exploring GxE. Full text in Research Archive
• Torvik, Fartein Ask; Eilertsen, Espen Moen; Ask, Helga; Gustavson, Kristin; McAdams, Tom A. & Ystrøm, Eivind (2019). Mechanisms linking parental education with symptoms of ADHD and depression in children. Behavior Genetics. ISSN 0001-8244. 49(6), p. 534–534. doi: 10.1007/s10519-019-09973-8. Full text in Research Archive
• McAdams, Tom A.; Hannigan, Laurie John; Eilertsen, Espen Moen; Gjerde, Line C.; Reichborn-Kjennerud, Ted & Eley, Thalia C. [Show all 8 contributors for this article] (2019). Is it time to reevaluate prenatal mental health? – Author's reply. The Lancet Psychiatry. ISSN 2215-0374. 6(2), p. 93–94. doi: 10.1016/S2215-0366(19)30004-5. Full text in Research Archive
• Ystrøm, Eivind; Eilertsen, Espen Moen; Gjerde, Line C.; Rijsdijk, Fruhling; Gustavson, Kristin & Ask, Helga [Show all 8 contributors for this article] (2018). Assortative mating and intergenerational transmission of ADHD. Behavior Genetics. ISSN 0001-8244. 48(6), p. 524–524. Full text in Research Archive
• Ystrøm, Eivind (2018). Norgesglasset - Hva er nevrositisme og hva kan vi gjøre for at det ikke slår ut i full blomst? [Radio]. NRK Radio. Full text in Research Archive
• Ystrøm, Eivind (2018). Professor ber foreldre stresse ned i oppdragelsen: «Det viktigste man overfører til sine barn, er genene». [Journal]. Aftenposten. Full text in Research Archive
• Ystrøm, Eivind (2018). Ett personlighetstrekk ligger bak nesten all psykisk sykdom. [Internet]. forskning.no. Full text in Research Archive
• Ystrøm, Eivind (2018). Recent Study Suggest Neuroticism is the Main Foundation for All Mental Illness. [Internet]. Daily News. Full text in Research Archive
• Ystrøm, Eivind (2018). Psykisk sjukdom beror på ett enda personlighetsdrag. [Journal]. Aftonbladet. Full text in Research Archive
• Mcadams, Tom; Hannigan, Laurie John; Eilertsen, Espen Moen; Gjerde, Line C.; Reichborn-Kjennerud, Ted & Eley, Thalia C. [Show all 8 contributors for this article] (2018). Maternal prenatal depression as a risk factor for early-life psychopathology in offspring: results from a genetically-informative, population-based sample. Full text in Research Archive
• Ystrøm, Eivind (2018). Intergenerational Transmission of Internalizing and Externalizing Psychopathological Spectra. Full text in Research Archive
• Ystrøm, Eivind (2018). Assortative mating, household effects, and family dynamics. Full text in Research Archive
• Ystrøm, Eivind; Eilertsen, Espen Moen; Gjerde, Line C.; Rijsdijk, Fruhling; Gustavson, Kristin & Ask, Helga [Show all 8 contributors for this article] (2018). Assortative mating and intergenerational transmission of ADHD. Full text in Research Archive
• Eilertsen, Espen Moen; Hannigan, Laurie John; McAdams, Tom A.; Rijsdijk, Fruhling; Czajkowski, Nikolai Olavi & Reichborn-Kjennerud, Ted [Show all 8 contributors for this article] (2018). Parental prenatal depression and offspring ADHD: a genetically informed intergenerational study. Behavior Genetics. ISSN 0001-8244. p. 469–469. Full text in Research Archive
• Eilertsen, Espen Moen; Hannigan, Laurie John; Mcadams, Tom; Rijsdijk, Fruhling; Czajkowski, Nikolai Olavi & Reichborn-Kjennerud, Ted [Show all 8 contributors for this article] (2018). Parental prenatal depression and offspring ADHD: A genetically informed intergenerational study. Full text in Research Archive
• Gjerde, Line C.; Eilertsen, Espen Moen; Rosenström, Tom Henrik; Reichborn-Kjennerud, Ted; McAdams, Tom A. & Eley, T.C. [Show all 7 contributors for this article] (2018). The genetic and environmental structure of psychopathology spectra in middle childhood. Behavior Genetics. ISSN 0001-8244. p. 473–474. Full text in Research Archive
• Gjerde, Line C.; Eilertsen, Espen Moen; Rosenström, Tom Henrik; Reichborn-Kjennerud, Ted; Røysamb, Espen & McAdams, Tom A. [Show all 8 contributors for this article] (2018). The Joint Structure of Psychopathology and Personality in Preadolescent Children – Preliminary Findings. Full text in Research Archive
• Lund, Ingunn Olea; Skurtveit, Svetlana; Handal, Marte; Bukten, Anne; Torvik, Fartein Ask & Ystrøm, Eivind [Show all 7 contributors for this article] (2018). Parental drinking and child long-term depression and anxiety: A longitudinal combined survey and registry study. Full text in Research Archive
• Villanger, Gro Dehli; Ystrøm, Eivind; Engel, Stephanie M.; Longnecker, Matthew P; Zoeller, R. Thomas & Pettersen, Rolf D. [Show all 12 contributors for this article] (2018). Neonatal thyroid stimulating hormone and relationship with childhood ADHD. Full text in Research Archive
• Abel, Marianne Hope; Ystrøm, Eivind; Caspersen, Ida Henriette; Aase, Heidi; Torheim, Liv Elin & Meltzer, Helle Margrete [Show all 9 contributors for this article] (2017). Maternal use of iodine-containing supplements in pregnancy is associated with increased risk of child attention-deficit/hyperactivity disorder. Full text in Research Archive
• Eilertsen, Espen Moen; Gjerde, Line C.; Rijsdijk, Fruhling; McAdams, Tom A. & Ystrøm, Eivind (2017). Disentangling genetic transmission from the environmental effect of maternal depression during pregnancy on offspring ADHD. Full text in Research Archive
• Gjerde, Line C.; Eilertsen, Espen Moen & Ystrøm, Eivind (2017). Hvordan går psykiske lidelser igjen i familier? En presentasjon av ITOR studien. Full text in Research Archive
• Ystrøm, Eivind (2017). Små barn våkner oftere hvis mor er deprimert. [Internet]. forskning.no. Full text in Research Archive
• Ystrøm, Eivind & Gjerde, Line C. (2017). Det man ikke kunne tro var sant om deprimerte mødre. Dagens medisin. ISSN 1501-4290. Full text in Research Archive
• Ystrøm, Eivind (2017). Det store søskenmysteriet. [Internet]. www.tine.no. Full text in Research Archive
• Lund, Ingunn Olea; Eilertsen, Espen Moen; Gjerde, Line C. & Ystrøm, Eivind (2017). Maternal alcohol consumption during 1st trimester and child internalizing and externalizing problems: A sibling control study. Full text in Research Archive
• Lund, Ingunn Olea; Eilertsen, Espen Moen; Gjerde, Line C.; Røysamb, Espen; Wood, Mollie & Reichborn-Kjennerud, Ted [Show all 7 contributors for this article] (2017). Prenatal Exposure to Alcohol and Child Internalizing and Externalizing Problems. Full text in Research Archive
• Rosenström, Tom Henrik; Czajkowski, Nikolai Olavi; Ystrøm, Eivind; Krueger, RF; Aggen, Steven H. & Gillespie, Nathan A. [Show all 9 contributors for this article] (2017). Stressful life events, antisocial and borderline personality traits, and alcohol use disorder: a genetically informative mediation study. Full text in Research Archive
• Rijsdijk, Frühling; Ystrøm, Eivind; Gjerde, Line C.; Eilertsen, Espen Moen & Mcadams, Tom (2017). Investigating Intergenerational Associations: Revisting the Children-of-Twins Design II. Full text in Research Archive
• Gjerde, Line C.; Eilertsen, Espen Moen; McAdams, Tom A.; Rijsdijk, Fruhling & Ystrøm, Eivind (2017). Disentangling the effects of maternal depressive symptoms to child internalizing and externalizing problems – an extended children of twins study. Full text in Research Archive
• Mcadams, Tom; Ystrøm, Eivind; Gjerde, Line C.; Eilertsen, Espen Moen & Rijsdijk, Frühling (2017). Investigating Intergenerational Associations: Revisiting the Children-of-Twins Design I. Full text in Research Archive
• Ystrøm, Eivind (2017). Gener styrer ofte vår alkoholbruk. [Journal]. Dagbladet. Full text in Research Archive
• Ystrøm, Eivind (2017). – Man tror man er Gud. At man er den som får personen ut av misbruket. [Journal]. Romerikes Blad. Full text in Research Archive
• Ystrøm, Eivind (2017). Det store søskenmysteriet. [Journal]. A-Magasinet. Full text in Research Archive
• Ystrøm, Eivind; Gustavson, Kristin; Brandlistuen, Ragnhild Eek; Knudsen, Gun Peggy; Magnus, Per & Susser, Ezra [Show all 14 contributors for this article] (2017). Acetaminophen exposure in pregnancy and offspring ADHD: familial risk and confounding by indication. Full text in Research Archive
• Ystrøm, Eivind (2017). Paracetamol exposure in pregnancy and offspring ADHD: familial risk and confounding by indication. Full text in Research Archive
• Ystrøm, Eivind (2017). Acetaminophen use during pregnancy and risk for ADHD. Full text in Research Archive
• Ystrøm, Eivind; Eilertsen, Espen Moen; Rijsdijk, Fruhling; Gjerde, Line C. & McAdams, Tom A. (2017). Intergenerational transmission of adult to child ADHD in a populationbased cohort study. Full text in Research Archive
• Ystrøm, Eivind; Rijsdijk, Fruhling; Gjerde, Line C.; Eilertsen, Espen Moen & McAdams, Tom A. (2017). Investigating intergenerational transmission of risk in a unique Norwegian extended twin-family sample. Full text in Research Archive
• Ystrøm, Eivind (2017). Intergenerasjonell overføring av personlighet og psykiske lidelser: en gjenganger. Full text in Research Archive
• Ystrøm, Eivind (2016). Paracetamol in pregnancy and offspring ADHD – challenges inferring causality. Full text in Research Archive
• Nesvåg, Ragnar; Ystrøm, Eivind & Kvåle, Gunnar (2016). Cannabis forverrer psykisk helse. Full text in Research Archive
• Ystrøm, Eivind (2016). Folkehelseinstituttet om fødselsdepresjon. [Radio]. Her og nå. Full text in Research Archive
• Ystrøm, Eivind (2016). Cannabis abuse possible cause of psychosis. [Internet]. ScienceDaily. Full text in Research Archive
• Ystrøm, Eivind (2016). Enebarn eller søskenflokk - hva er best? [Journal]. Bergens Tidende. Full text in Research Archive
• Ystrøm, Eivind (2016). Norsk studie: Cannabismisbruk tredobler risiko for psykose. [Journal]. Aftenposten. Full text in Research Archive
• Ystrøm, Eivind (2016). Sant og usant om psykisk helse – perspektiv fra en psykolog. Full text in Research Archive
• Ystrøm, Eivind (2016). Foreldrene er årsaken til at unge får sosialstønad. [Internet]. forskning.no. Full text in Research Archive
• Ystrøm, Eivind (2016). De fleste som får sosialhjelp har ikke selv skyld i at de har kommet i den situasjonen. [Radio]. NRK Radio - Her og Nå. Full text in Research Archive
• Brandlistuen, Ragnhild Eek; Ystrøm, Eivind; Nulman, Irena; Koren, Gideon & Nordeng, Hedvig Marie Egeland (2015). Annotations and Reflections: Response to “Pregnancy and Paracetamol: Methodological Considerations on the Study of Associations between In Utero Exposure to Drugs and Childhood Neurodevelopment”. Basic & Clinical Pharmacology & Toxicology. ISSN 1742-7835. 116(1), p. 6–8. doi: 10.1111/bcpt.12339. Full text in Research Archive
• Nordeng, Hedvig Marie Egeland; Wood, Mollie; Frazier, Jean; Lapane, Kate L.; Ystrøm, Eivind & Mick, Eric O. (2015). Prenatal triptan exposure increases externalizing behaviors at three years: results from the Norwegian Mother and Child Cohort Study. Full text in Research Archive
• Brandlistuen, Ragnhild Eek; Ystrøm, Eivind; Eberhard-Gran, Malin; Nulman, Irena; Koren, Gideon & Nordeng, Hedvig Marie Egeland (2015). Behavioural effects of fetal antidepressant exposure in a Norwegian cohort of discordant siblings. Full text in Research Archive
• Gjerde, Line C.; Eilertsen, Espen Moen; Reichborn-Kjennerud, Ted & Ystrøm, Eivind (2015). IToR - a novel, prospective extended children of twins study. Full text in Research Archive
• Eilertsen, Espen Moen; Gjerde, Line C.; Reichborn-Kjennerud, Ted & Ystrøm, Eivind (2015). Maternal alcohol use during pregnancy and offspring ADHD. Full text in Research Archive
• Ebeltoft, Joakim; Ystrom, Eivind; Eilertsen, Espen Moen & Ayorech, Ziada (2026). Dissecting intergenerational patterns of socioeconomic status and mental disorders in Norway. Universitetet i Oslo. Full text in Research Archive Show summary

  Socioeconomic status (SES) and mental disorders run in families—representing intergenerational persistence of advantages and disadvantages. Through three original research studies, this thesis investigates intergenerational patterns of socioeconomic status and mental disorders in Norway using genetically informed designs. First, in paper 1, I explore the coarse-grained etiology of the “big four” SES indicators —education, income, occupation, and wealth. By triangulating four advanced genetic methods, I demonstrate common and unique genetic and environmental sources of variance in parent SES. The substantial common variation across the “big four” is linked to genetic and shared environmental influences, while the considerable unique variance is explained by non-shared environment variation. Second, in paper 2, I assess the risk of mental disorders in young people given their parents’ SES—wealth in particular. In multivariable models including the “big four,” parental wealth is the strongest predictor of most mental disorder diagnoses in children, adolescents, and young adults. Significant associations between parent wealth and risk of mental disorders in young people persist after controlling for sibling-shared genetic and environmental factors. Third, in paper 3, I investigate the effects of children’s genetic differences on parents’ economic outcomes from 3 years before birth to 15 years after birth. By controlling for parent genetic factors, child genetic effects were identified using two methods. We found no conclusive evidence of child genetic effects on parent income, wealth, and government transfers. Three broad causal models can explain SES and mental disorder outcome correlations between parents (X) and their children (Y): A) third factors causing correlated observations (X←Z→Y), B) parent factors causing child outcomes (X→Y), and C) child factors causing parent outcomes (X←Y). Paper 1 provides evidence of model A, showing how common genetic and environmental factors explain large shares of the variance between the “big four” SES indicators. Paper 2 provides evidence of both model A and B, indicating that both shared genetic and environmental factors and parental wealth influence mental disorder risk in their children. Paper 3 provides inconclusive evidence of model C child genetic effects on their parents’ economic outcomes. This thesis argues that genetically informed designs are valuable for dissecting at least three important conceptual angles with regard to intergenerational patterns of SES and mental disorders: (i) genetic architecture as the focus—estimating the relative magnitude genetic contributions to phenotypes, and genetic correlations between phenotypes (paper 1); (ii) genetics as a confounder—estimating social effects while accounting for genetic similarity in families (papers 2 and 3), (iii) genetics as a proxy for a social effect—estimating socially-mediated genetic influences on another person’s phenotype (paper 3).

• Peng, Qiyuan; Eilertsen, Espen Moen; Cheesman, Rosa Catherine Gillespie; Rietveld, Cornelius A.; Ystrom, Eivind & Havdahl, Alexandra (2025). Parental Influence on Children’s Educational Achievements: Analysing Direct and Indirect Genetic Effects through Trio-GCTA. bioRxiv. doi: https:/www.biorxiv.org/content/10.64898/2025.12.03.691991v1.article-info. Full text in Research Archive Show summary

  Educational achievement is a key predictor of later-life outcomes, including financial security, social mobility, health, and mortality. Knowing its familial determinants, such as genetic predispositions, is crucial for understanding intergenerational educational mobility and addressing educational inequality. Here, we disentangle direct and indirect genetic effects on educational achievement using trio genome-wide complex trait analysis (Trio-GCTA). Leveraging up to 23,200 genotyped parent–offspring trios from the Norwegian Mother, Father, and Child Cohort Study (MoBa), we find that direct genetic effects explain 15-21% of the variance in educational achievements, including 8th-grade national assessments in Math, Reading, and English, and 10th-grade grade point average (GPA). Notably, indirect genetic effects additionally explain 7-15% of the variance. Both mothers and fathers exert notable influences, exceeding those suggested in previous studies. Moreover, positive gene–environment correlations between parents and offspring show that the intrafamilial environment and children’s genetic predisposition are dependent and mutually reinforcing.

• Samuelsen, Kristin; Ystrøm, Eivind; Eilertsen, Espen Moen & Gjerde, Line Cecilie (2019). Emerging Genetic and Environmental Risk Factors for Prenatal and Postnatal Depression. Universitetet i Oslo. Full text in Research Archive Show summary

  Author: Kristin Samuelsen. Title: Emerging Genetic and Environmental Risk Factors for Prenatal and Postnatal Depression. Supervisors: Main supervisor Eivind Ystrøm, and co-supervisors Line C. Gjerde and Espen M. Eilertsen. Background: Many women experience depression both during pregnancy (prenatal) and following delivery (postnatal). Although there is some literature on risk factors, there is a lack of studies investigating heritability. Thus, it is largely unknown to what extent genetic and environmental factors contribute to depression at these time points, as well as whether they are similar across timing. Research on these questions may yield important insights into whether depression prior to and following childbirth is the same, similar or distinct constructs. Research aims: 1) Estimate the relative importance of genetic and environmental factors for depression during and after pregnancy, and 2) Estimate the genetic and environmental correlation between depression during and after pregnancy, i.e. estimate the extent of genetic innovation. Sample: The sample used in this study is a subsample of the prospective, ongoing pregnancy cohort study Norwegian Mother and Child Cohort Study (MoBa), conducted by the Norwegian Institute of Public Health (N = 64 monozygotic (MZ) twin pairs, 35 dizygotic (DZ) twin pairs, 5540 full sibling (FS) pairs, and 400 half siblings (HS) pairs. Research design: A quantitative, extended twin study design, including siblings was applied. Methods: Measurement was conducted at week 30 of pregnancy and 6 months following delivery, using SCL-8, an abbreviated version of SCL-90. Univariate and bivariate twin modeling was conducted. Results: The relative importance of genes and environment for prenatal depressive symptoms was estimated at 16.2%, and 83.8%, respectively, and at 25.7% and 74.3% postnatally. Estimated correlation between pre and postnatal depressive symptoms was at 1.00 for genetic effects, and .36 for environmental effects. The unstandardized genetic effects for postnatal depressive symptoms were 172% of that of prenatal depressive symptoms, showing a quantitative, but a lack of a qualitative, gene-environment interaction (GxE). That is, the same genetic factors had a stronger impact postnatally. Conclusions: The findings indicate that the most important risk factors for pre and postnatal depression are environmental in their nature, yet they appear to be different dependent on the timing. The same genetic factors appear to influence depression at both time points, but to a stronger degree postnatally. This implicates that prevention efforts to depression occurring at this time should be predominantly aimed at reducing environmental stressors of depression specific to each timing.

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