GeoGen The PsychoGeography of Intergenerational Mobility

• 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
• 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.

• 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
• Cheesman, Rosa Catherine Gillespie; Borgen, Nicolai T.; Sandsør, Astrid Marie Jorde & Hufe, Paul (2025). The Genetic Lottery Goes to School: Better Schools Compensate for the Effects of Students' Genetic Differences. Proceedings of the National Academy of Sciences of the United States of America (PNAS). ISSN 0027-8424. 122(43). doi: 10.1073/pnas.2511715122. Full text in Research Archive Show summary

  In this paper, we investigate whether better schools can compensate for the effects of children’s genetic differences. To this end, we combine data from the Norwegian Mother, Father, and Child Cohort Study (MoBa) with Norwegian register data to estimate the interaction between measures of children’s predisposition to education and school quality. We use MoBa’s genetic data to compute polygenic indices for educational attainment (PGIEA). Importantly, MoBa includes genetic data on mother-father-child trios, allowing us to identify causal genetic effects using within-family variation. We calculate school value-added measures from Norwegian register data, allowing us to causally estimate school quality effects. Leveraging the advantages of both data sources, we provide a causally identified study of gene–environment interactions in the school context. We find evidence for substitutability of PGIEA and school quality in reading but not numeracy: A 1 SD increase of school quality decreases the impact of a 1 SD increase of PGIEA on reading test scores by 6%. The substitutability arises through gains of students at the lower end of the PGIEA distribution. This suggests that investments in school quality may help reduce educational inequalities arising from genetic differences between students.

• 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.

• Hootegem, Arno Van; Rogne, Adrian Farner; Cros, Caroline Tveter; Røgeberg, Ole Jørgen & Lyngstad, Torkild Hovde (2025). Social origins and socioeconomic outcomes: a combined twin and adoption study. European Sociological Review. ISSN 0266-7215. 41(5), p. 793–807. doi: 10.1093/esr/jcaf029. Full text in Research Archive Show summary

  Parents and children tend to have similar socioeconomic status (SES). Sociological theory has often emphasized the role of social mechanisms in intergenerational transmission, including the influence of the broader rearing environment as well as parental investments and aid, but often not allotted an important role to genetics. Accumulating evidence suggests that genetics play an important role in the transmission of SES from parents to children. Yet, estimates differ substantially across data sets, measures and methods. Using two research designs that account for potential genetic confounding, and high-quality data from Norway, we estimate the strength of the intergenerational social transmission of a range of SES indicators. By triangulating data and designs, we obtain estimates that are more robust to idiosyncratic modelling assumptions. Measures of Norwegian parents’ socioeconomic position predict their children’s socioeconomic outcomes, but purely social mechanisms only account for a fifth of the total explained variance in intergenerational transmission.

• Demange, Perline Aline Delle; Boomsma, Dorret; Bergen, Elsje van & Nivard, Michel (2024). Educational attainment and psychiatric diagnoses: a national registry data and two-sample Mendelian randomization study. Nature Communications. 2(6), p. 668–679. doi: 10.1038/s44220-024-00245-x. Full text in Research Archive
• 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
• 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.

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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 (2026). Beyond trio: genetic effects in the extended family. Full text in Research Archive
• Demange, Perline Aline Delle (2026). Beyond trio: genetic effects in the extended family. 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
• Demange, Perline Aline Delle (2026). Cognitive, Non-Cognitive, and Genetics: Perline Demange on Skills, Schooling, and Psychopathology. 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.

• 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.

• 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.

• Demange, Perline Aline Delle (2025). Beyond trio: genetic effects in the extended family. Full text in Research Archive
• Demange, Perline Aline Delle (2025). Beyond trio: genetic effects in the extended family. Full text in Research Archive
• 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.

• 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.

• 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.

• Demange, Perline Aline Delle (2025). Beyond trio: genetic effects in the entire extended family. Full text in Research Archive
• 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.

• Cheesman, Rosa Catherine Gillespie; Zachrisson, Henrik Daae & Bailey, Drew (2025). Gene-environment interplay and childcare decisions. Full text in Research Archive
• 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
• 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
• 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.

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