Causes, consequences, and life-course trajectories of personality pathology - a longitudinal extended children-of-twins study

Duration: 01.12.2021–30.09.2027

Contact

Nikolai Olavi Czajkowski Principal investigator

About the project

Personality pathology can manifest in very different ways, as extreme distrust and paranoia, emotional volatility, reckless disregard for the wellbeing of others, crippling perfectionism or social inhibition.

Since personality pathology can have a detrimental impact on virtually all social interactions, the risk of distress and negative outcomes also extends to people in close relationships with those afflicted, in particular their spouses and children.

With this study we aim to better understand how personality pathology changes through life, and what long-term psychosocial outcomes they lead to. We also want to shed light on the underlying causes of pathological personality, how they influence other members within families.

Objectives

To investigate the developmental trajectories of personality pathology from early to middle adulthood, determine the degrees of stable and time varying etiological factors, and their longitudinal relationship with clinical disorders.
Evaluate life-course functional, psychosocial and health outcomes of personality pathology, as evidenced by information from Norwegian national registries.
Determine the processes by which personality pathology and clinical disorders in parents increase the risk of ill mental health and negative psychosocial outcomes in offspring, and visa versa.

Methods

In addition to using data from previous waves of the study, we will also conduct a major new round of data collection. This time we will not only invite twins from the original 1969-79 cohort, but also their partners, non-twin siblings, and children over 16 years. In addition, we will make use of the rich data in Norwegian national registries to assess life-course outcomes.

Since people with pathological personality traits, such as avoidant or antisocial traits, often decline to participate in research studies, an important part of this study will be to investigate personality disorders using registry data from the complete 1967-79 cohort of Norwegian citizens, as well as their close relatives. This gives us a unique opportunity not only to tackle non-response in our data collections, but also to critically evaluate the assumptions underlying twin studies.

Participants

Nikolai Olavi Czajkowski University of Oslo Principal investigator
Eivind Ystrøm University of Oslo
Mathias Valstad University of Oslo
Tianfang Yang University of Oslo

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
Prydz, Monica Beer; Bjørndal, Ludvig Daae; Czajkowski, Nikolai Olavi; Røysamb, Espen & Nes, Ragnhild Bang (2025). Direct and indirect effects of a digital Five Ways to Wellbeing intervention: A network intervention analysis. Behaviour Research and Therapy. ISSN 0005-7967. 191. doi: 10.1016/j.brat.2025.104781. Full text in Research Archive Show summary
While digital positive psychology interventions demonstrate effectiveness in promoting wellbeing and reducing illbeing in the general population, their pathways of change are relatively underexplored. The wellbeing promotive digital intervention, Five Ways to Wellbeing for All (5waysA), has been shown effective (Cohens’ d effect sizes from .20 to .49) in a large (N = 963) randomized controlled trial (Prydz et al., 2024). In the present study, network intervention analysis (NIA) was applied to identify putative direct and indirect effects linking the 5waysA intervention to a set of wellbeing outcomes. Following the 10-week intervention period, the NIA revealed that only positive emotions on an aggregate level were conditionally dependent on the treatment allocation variable. These findings suggest that the effectiveness of the 5waysA intervention primarily reflects the direct enhancement of positive emotions. Our findings provide insights of potential importance for advancing the theoretical framework of the Five Ways to Wellbeing and other mental health and wellbeing promoting interventions.
Arneberg, Vilde Sofie; Sundsvold, Vilde; Bjørndal, Ludvig Daae & Ystrøm, Eivind (2024). Borderline Personality Disorder Symptoms and Stressful Life Events: An Evaluation of Gene-Environment Interplay. Biological Psychiatry: Global Open Science. 4(6). doi: 10.1016/j.bpsgos.2024.100390. Full text in Research Archive Show summary
Background Borderline personality disorder (BPD) is associated with high rates of stressful life events (SLEs). It is unclear whether people who experience SLEs have more BPD symptoms after accounting for the effects of familial risk factors. Our aims in the current study were to 1) create a predictive model of BPD using stressors across age and contexts and 2) examine whether SLEs resulted in higher levels of BPD symptoms beyond the effects of genetic and environmental risk factors. Methods The sample comprised 2801 twins from the Norwegian Institute of Public Health Twin Panel. Poisson regression was used to explore which SLEs predicted BPD symptoms. Elastic net penalized regression was conducted to develop a predictive model for SLEs and BPD symptoms. Co-twin control analyses were performed to differentiate between environmental and genetic factors. Results SLEs experienced during childhood and adulthood were associated with BPD symptoms. A weighted polyevent risk score explained 22% of the total variation in symptoms. Shared environmental and heritable factors explained 31% and 47% of individual differences in BPD symptomatology, respectively. Measured SLEs explained 42% of the shared environmental risk for BPD. The predictive risk of SLEs for BPD was reduced when shared environmental and genetic factors were accounted for. However, SLEs increased risk of BPD symptoms beyond the effects of shared genetic and environmental factors. Conclusions BPD symptomatology following SLEs cannot fully be explained by genetic and shared environmental factors. The SLE-BPD symptoms associations were primarily due to selection by family environments. It is important to identify familial factors that lead to both SLEs and BPD symptoms. SLEs remained associated with BPD symptoms beyond genetic and environmental confounding.
Bjørndal, Ludvig Daae; Nes, Ragnhild Bang; Czajkowski, Nikolai Olavi & Røysamb, Espen (2023). The structure of well-being: a single underlying factor with genetic and environmental influences. Quality of Life Research. ISSN 0962-9343. 32, p. 2805–2816. doi: 10.1007/s11136-023-03437-7. Full text in Research Archive
Tesli, Martin Steen; Nesvåg, Ragnar; Haukvik, Unn Kristin Hansen; Gustavson, Kristin; Tesli, Natalia & Friestad, Christine [Show all 12 contributors for this article] (2023). Common genetic and environmental risk for personality disorders and psychotic-like experiences in young adult twins. Acta Psychiatrica Scandinavica. ISSN 0001-690X. 148(6), p. 561–569. doi: 10.1111/acps.13596. Full text in Research Archive Show summary
Abstract Introduction Psychotic‐like experiences (PLE) have been associated with the subsequent emergence of psychotic disorders as well as several other domains of psychopathology. In this twin study, we estimated the genetic and environmental correlations between PLE and 10 personality disorders (PD). Methods Diagnoses of 10 PDs according to the Diagnostic and Statistical Manual of Mental Disorders (DSM‐IV) and PLE from the Composite International Diagnostic Interview (CIDI) were retrieved for 2793 young adult twins from the Norwegian Twin Registry. Risk for having a PD and PLEs was modeled using item response theory. Biometric twin models were fitted to estimate the genetic and environmental correlations between PDs and PLEs. Co‐twin control analysis was performed to estimate additional within‐family risk for PLEs when having a PD. Results Phenotypic overlap between PDs and PLEs ranged from 14% to 44% in males and from 11% to 39% in females, with the highest overlap for borderline PD in both sexes. In general, we found higher genetic correlations ( r = 0.14–0.72) than environmental correlations ( r = 0.06–0.28) between PDs and PLEs. The highest genetic correlations between PLE and PDs were found for borderline ( r = 0.72), paranoid ( r = 0.56), schizotypal ( r = 0.56) and antisocial PD (r = 0.49). Conclusion We found that the co‐occurrence between PDs and PLE is the best explained by shared genetic determinants, with minor contributions from environmental factors. Interestingly, borderline PD was highly genetically correlated with PLE, warranting molecular genetic studies of this association.
Eftedal, Nikolai Haahjem; Kleppestø, Thomas Haarklau; Czajkowski, Nikolai Olavi; Sheehy-Skeffington, Jennifer; Røysamb, Espen & Vassend, Olav Mandt [Show all 8 contributors for this article] (2022). Justice sensitivity is undergirded by separate heritable motivations to be morally principled and opportunistic. Scientific Reports. 12. doi: 10.1038/s41598-022-09253-2. Full text in Research Archive Show summary
Abstract Injustice typically involves some people benefitting at the expense of others. An opportunist might then be selectively motivated to amend only the injustice that is harmful to them, while someone more principled would respond consistently regardless of whether they stand to gain or lose. Here, we disentangle such principled and opportunistic motives towards injustice. With a sample of 312 monozygotic- and 298 dizygotic twin pairs (N = 1220), we measured people’s propensity to perceive injustice as victims, observers, beneficiaries, and perpetrators of injustice, using the Justice Sensitivity scale. With a biometric approach to factor analysis, that provides increased stringency in inferring latent psychological traits, we find evidence for two substantially heritable factors explaining correlations between Justice Sensitivity facets. We interpret these factors as principled justice sensitivity (h 2 = 0.45) leading to increased sensitivity to injustices of all categories, and opportunistic justice sensitivity (h 2 = 0.69) associated with increased sensitivity to being a victim and a decreased propensity to see oneself as a perpetrator. These novel latent constructs share genetic substrate with psychological characteristics that sustain broad coordination strategies that capture the dynamic tension between honest cooperation versus dominance and defection, namely altruism, interpersonal trust, agreeableness, Social Dominance Orientation and opposition to immigration and foreign aid.
Skaug, Eirunn; Czajkowski, Nikolai Olavi; Waaktaar, Trine & Torgersen, Svenn (2022). The role of sense of coherence and loneliness in borderline personality disorder traits: a longitudinal twin study. Borderline Personality Disorder and Emotion Dysregulation. 9. doi: 10.1186/s40479-022-00190-0. Full text in Research Archive Show summary
Background Borderline personality disorder (BPD) implies having problems with identity and relations with other people. However, not much is known about whether these indications of BPD are present in adolescence, i.e., before personality disorders usually are diagnosed. In this study, we examined the prediction of an aspect of identity (i.e., sense of coherence [SOC]) and social relations (i.e., perceived loneliness) throughout adolescence on BPD traits in young adulthood. In addition, we examined to what degree the predictive ability could be attributed to genetic and environmental factors. We also examined whether life events in adolescence were related to BPD traits. Methods Three thousand three hundred ninety-one twins, consisting of seven national birth cohorts from Norway, participated in the study. SOC, loneliness and life events were measured three times throughout adolescence with self-report questionnaires, with 2 years in between measurements. BPD traits were measured at the end of adolescence around the age of 19 with a structured interview. Regression analyses were performed to examine the prediction of SOC, loneliness and life events on BPD traits. Cholesky decomposition models were then used to determine to what degree the associations were due to genetic and environmental influences. Results The prediction of SOC and loneliness on BPD traits increased from R = .25 (when measured 6 years prior to the assessment of BPD traits) to R = .45 (when measured shortly before the assessment of BPD traits). In addition, negative life events considered dependent on a person’s behavior were related to BPD traits. Negative independent and positive dependent life events did not contribute to the prediction of BPD traits. Cholesky decomposition models showed that SOC and loneliness were associated with BPD traits mainly due to shared genetic influences (i.e., the proportion due to genetic influences ranged from 71 to 86%). Adding negative dependent life events to the prediction of BPD traits did not change these percentages. Conclusions These findings indicate that the weaker SOC, the stronger feelings of loneliness, and the negative life events associated with BPD traits are mainly consequences of the genetic aspects of BPD traits, rather than having direct effects on levels of BPD symptoms.
Skaug, Eirunn; Czajkowski, Nikolai Olavi; Waaktaar, Trine & Torgersen, Svenn (2022). Childhood Trauma and Borderline Personality Disorder Traits: A Discordant Twin Study. Journal of Psychopathology and Clinical Science. ISSN 2769-7541. 131(4), p. 365–374. doi: 10.1037/abn0000755. Full text in Research Archive
Skaug, Eirunn; Czajkowski, Nikolai Olavi; Waaktaar, Trine & Torgersen, Svenn (2022). The relationship between life events and sense of coherence in adolescence. A longitudinal twin study. Journal of Research in Personality. ISSN 0092-6566. 99. doi: 10.1016/j.jrp.2022.104259. Full text in Research Archive Show summary
This three-wave study examined the relationship between life events and sense of coherence (SOC) throughout adolescence by using genetically informative random intercept cross-lagged panel models. We also examined the genetic and environmental contribution to variance in the measured constructs. The data come from a Norwegian population-based twin sample (N = 2,878). Life events and SOC were associated, and both showed substantial genetic variance. Negative longitudinal effects were observed from negative dependent life events to SOC, from SOC to negative dependent life events and from SOC to positive dependent life events. However, these longitudinal effects were negligible in magnitude. In summary, the associations between all three clusters of life events and SOC were almost completely accounted for by shared genetic influences.
Vassend, Olav Mandt; Czajkowski, Nikolai Olavi; Røysamb, Espen & Nielsen, Christopher Sivert (2022). The role of neuroticism and pain in dental anxiety: A twin study. Community Dentistry and Oral Epidemiology. ISSN 0301-5661. doi: 10.1111/cdoe.12763. Full text in Research Archive Show summary
Objectives Accumulating evidence has revealed that dental anxiety is robustly associated with dental care-related pain and discomfort, but also with the personality trait of neuroticism (i.e. the relatively stable disposition to experience the world as distressing, threatening and unsafe). However, there is a near absence of research on these risk factors in samples for which genetic information is available. With the aim of arriving at a more refined understanding of dental anxiety, this twin cohort study assessed genetic and environmental influences on neuroticism, dental care-related pain and dental anxiety, and the relation between these phenotypes. Methods Participants were recruited from the Norwegian Twin Registry, and data collections were carried out in 1992–98 (Time 1) and 2011 (Time 2). Well-validated questionnaires were used to assess the study variables, including Corah's Dental Anxiety Scale, the Numerical Pain Rating Scale, the NEO Personality Inventory Revised (Time 2) and Eysenck's Personality Questionnaire (Time 1). Pearson correlation analysis and generalized estimating equations (GEE) were used to investigate phenotypic associations. Analyses of genetic and environmental influences were performed using Cholesky modelling. Results A total of 746 monozygotic (MZ) and 770 dizygotic (DZ) twins in the age group of 50–65 participated in the study. Moderate estimates of heritability for dental anxiety (0.29), treatment-related pain (0.24) and neuroticism (0.45–0.54) were found. Cholesky modelling showed furthermore that neuroticism assessed at Time 1 and Time 2 was related to dental anxiety and pain via both genetic and individual-specific environmental pathways, albeit not very strongly. The particularly high phenotypic correlation observed between dental care-related pain and anxiety (r = .68) was explained by both overlapping genetic and individual-specific environmental influences (the genetic and environmental correlations were .84 and .63 respectively). Conclusions The findings provide deeper insight into the aetiology of dental anxiety and confirm that while it is strongly linked to treatment-related pain experiences, this relation is to a considerable degree independent of general negative affectivity/neuroticism.

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Yang, Tianfang; Anderson, Jacob; Corley, Robin; Hopfer, Christian; McGue, Matt & Rhee, Soo [Show all 10 contributors for this article] (2026). Linking Pathological Personality Trait to Parenting, Romantic Relationship, and Workplace Behaviors: Using Co-Twin Control to Understand Variances in Pathways. Full text in Research Archive
Yang, Tianfang; Anderson, Jacob E.; Corley, Robin P.; Hopfer, Christian J.; McGue, Matt K. & Rhee, Soo [Show all 11 contributors for this article] (2026). Etiologic Links Between Personality Pathology and Workplace Behavior. Full text in Research Archive
Yang, Tianfang; Anderson, Jacob E.; Corley, Robin P.; Hopfer, Christian J.; McGue, Matt K. & Rhee, Soo [Show all 11 contributors for this article] (2026). Linking pathological personality trait to workplace behaviors: using co-twin control to understand pathways. Full text in Research Archive
Yang, Tianfang; Nikolic, Milena; Grønnerød, Cato & Czajkowski, Nikolai Olavi (2026). A Person-Centered Examination on the Overlap Between Maladaptive and Normal Personality Profiles: Evidence from Norwegian Community Sample. 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?
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.
Yang, Tianfang; Eftedal, Nikolai Haahjem; Valstad, Mathias; Reichborn-Kjennerud, Ted; Ystrom, Eivind & Czajkowski, Nikolai Olavi (2025). The lifespan impact of personality disorder on marital outcome: a Norwegian population study. Full text in Research Archive
Czajkowski, Nikolai Olavi; Gustavson, Kristin & Ystrom, Eivind (2025). When Dracula Takes the PID-5: What Can We Learn from Psychometric Exploration of Data Simulated Using Large Language Models. Full text in Research Archive Show summary
Several recent studies have demonstrated that large language models (LLMs) are able to simulate responses to surveys in ways that mimic observed characteristics of data from real human samples (Argyle, 2023). Since LLMs are trained on a sizeable proportion of all text produced by humans, it is reasonable to expect that they capture a deep understanding of human personality traits. Consequently, analysing data simulated by LLM’s may enable new ways to study psychological constructs and develop psychometric instruments. In this exploratory study, we used the GPT programming interface (API) to prompt the model to generate responses for 300 well-known literary characters across several instruments related to pathological and normative personality traits. This included the PID-5, the Structured Interview for DSM-5 Personality Disorders (SIDP), the Big Five Inventory-2 (BFI-2), and the IPIP-300. Characters were drawn from a wide range of literary traditions, genres, and historical periods. For each instrument, GPT-4o was instructed to adopt the voice and perspective of the character and provide item-level responses using standard Likert-style scales. Our goal was twofold: first, to assess whether the factor structures and inter-scale correlations observed in the simulated data resembled those from real-world samples; and second, to explore whether the same data might suggest novel trait constellations or latent domains not fully captured by existing instruments. Together, these analyses offer a proof of concept for using LLMs in hypothesis generation and instrument development.
Czajkowski, Nikolai Olavi; Solbakken, Ole Andre; Stenberg, Jan-Henry; Suoma, Saarni E. & Rosenström, Tom Henrik (2025). Evaluating Internet-Based CBT for Depression in Patients with Prior Borderline Personality Disorder: Evidence from Finnish Registry Data. Full text in Research Archive Show summary
Internet-based cognitive behavioral therapy (iCBT) has demonstrated comparable effectiveness to traditional psychotherapy for mild to moderate depression, as shown in a recent large-scale Finnish registry study (Rosenström et al., 2025). In routine care, patients with comorbid borderline personality disorder (BPD) are often referred to more intensive treatment formats, and registry data suggest they receive significantly more psychotherapy sessions than individuals with depression alone, even when symptom severity is comparable (van Bronswijk et al., 2021). Findings such as this may contribute to clinicians hesitating to offer low-intensity treatments, such as iCBT, to patients with current or prior BPD diagnoses. However, to our knowledge, no studies have directly assessed whether a history of BPD is associated with reduced effectiveness of iCBT for depression. In this study, we will use data from the HUS-iCBT registry and the Finnish Psychotherapy Quality Register (FPQR) to investigate whether: A BPD diagnosis (ICD-10 F60.3) moderates the effectiveness of iCBT for depression. Conventional face-to-face CBT (fCBT) yields superior outcomes for patients with prior BPD compared to iCBT. BPD is associated with increased dropout in iCBT. Our analyses will focus on patients diagnosed with mild to moderate depressive episodes (ICD-10 F32.0–F32.1), with symptom severity assessed using the PHQ-9 or BDI. Linear mixed-effects models will test for moderation effects, compare outcomes between iCBT and fCBT, and examine dropout patterns by diagnostic subgroup.
Valstad, Mathias; Eftedal, Nikolai Haahjem; Yang, Tianfang; Reichborn-Kjennerud, Ted; Ystrom, Eivind & Czajkowski, Nikolai Olavi (2025). Epidemiology of personality disorders in Norway, 2010 to 2022. Full text in Research Archive
Czajkowski, Nikolai Olavi; Eilertsen, Espen Moen; Valstad, Mathias; Eftedal, Nikolai Haahjem & Ystrøm, Eivind (2025). A Bayesian Framework for Zygosity Classification and Heritability Estimation Using Nationwide Registry Data. Full text in Research Archive
Yang, Tianfang; Ystrøm, Eivind; Valstad, Mathias; Eftedal, Nikolai Haahjem; Reichborn-Kjennerud, Ted & Czajkowski, Nikolai Olavi (2025). Marital Consequence of Personality Disorder: Evidence from Norwegian Registry. Full text in Research Archive
Yang, Tianfang; Ystrøm, Eivind; Valstad, Mathias; Eftedal, Nikolai Haahjem; Reichborn-Kjennerud, Ted & Krueger, Robert F [Show all 7 contributors for this article] (2024). The Intergenerational Impact of Borderline and Avoidant Personality Disorders on Child Academic Achievement: A Registry Study in Norway. Full text in Research Archive
Czajkowski, Nikolai Olavi; Eftedal, Nikolai Haahjem; Yang, Tianfang; Valstad, Mathias; Reichborn-Kjennerud, Ted & Ystrøm, Eivind (2024). The Role of Parental Personality Disorders in High School Dropout: Insights from a Nationwide Cohort Study. Full text in Research Archive
Valstad, Mathias; Eilertsen, Espen Moen; Timpe, Clara Marie Fides; Yang, Tianfang; Eftedal, Nikolai Haahjem & Reichborn-Kjennerud, Ted [Show all 8 contributors for this article] (2024). Genetic and environmental effects on diagnosed Borderline Personality Disorder (BPD) without clinic bias. Full text in Research Archive
Ystrøm, Eivind (2024). Gene-Environment Interplay and Borderline Personality Disorder Symptoms Amid Stressful Life Events. Full text in Research Archive

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Funding

Project number: 326350

Published Jan. 22, 2025 8:43 AM - Last modified Sep. 11, 2025 12:03 PM