Unravelling the interplay between genetic and environmental contributions in the unfolding of personality differences from early adolescence to young adulthood

Kandler C, Waaktaar T, Mottus R, Riemann R, Torgersen S. Unravelling the Interplay Between Genetic and Environmental Contributions in the Unfolding of Personality Differences from Early Adolescence to Young Adulthood. EUROPEAN JOURNAL OF PERSONALITY. 2019;33(3):221-244.In two studies, we examined the genetic and environmental sources of the unfolding of personality trait differences from childhood to emerging adulthood. Using self-reports from over 3000 representative German twin pairs of three birth cohorts, we could replicate previous findings on the primary role of genetic sources accounting for the unfolding of inter-individual differences in personality traits and stabilizing trait differences during adolescence. More specifically, the genetic variance increased between early (ages 10-12 years) and late (ages 16-18 years) adolescence and stabilized between late adolescence and young adulthood (ages 21-25 years). This trend could be confirmed in a second three-wave longitudinal study of adolescents' personality self-reports and parent ratings from about 1400 Norwegian twin families (average ages between 15 and 20 years). Moreover, the longitudinal study provided evidence for increasing genetic differences being primarily due to accumulation of novel genetic influences instead of an amplification of initial genetic variation. This is in line with cumulative interaction effects between twins' correlated genetic makeups and environmental circumstances shared by adolescent twins reared together. In other words, nature x nurture interactions rather than transactions can account for increases in genetic variance and thus personality variance during adolescence. (c) 2019 European Association of Personality Psycholog

Genetic and Environmental Causes of Variation in Trait Resilience in Young People

The aim of this multi-informant twin study was to determine the relative role of genetic and environmental factors in explaining variation in trait resilience in adolescents. Participants were consenting families (N = 2,638 twins in 1,394 families), from seven national cohorts (age 12–18 years, both sexes) of monozygotic and dizygotic twins reared together. Questionnaire data on the adolescents’ Ego-resilience (ER89) was collected from mothers, fathers and twins, and analysed by means of multivariate genetic modelling. Variance in trait resilience was best represented in an ADE common pathways model with sex limitation. Variance in the latent psychometric resilience factor was largely explained by additive genetic factors (77% in boys, 70% in girls), with the remaining variance (23 and 30%) attributable to non-shared environmental factors. Additive genetic sources explained more than 50% of the informant specific variation in mothers and fathers scores. In twins, additive and non-additive genetic factors together explained 40% and non-shared environmental factor the remaining 60% of variation. In the mothers’ scores, the additive genetic effect was larger for boys than for girls. The non-additive genetic factor found in the twins’ self ratings was larger in boys than in girls. The remaining sex differences in the specific factors were small. Trait resilience is largely genetically determined. Estimates based on several informants rather than single informants approaches are recommended

The genetic and environmental architecture of substance use development from early adolescence into young adulthood: a longitudinal twin study of comorbidity of alcohol, tobacco and illicit drug use

This is the peer reviewed version of the following article: Waaktaar, T., Kan, K.-J., and Torgersen, S. (2017) The genetic and environmental architecture of substance use development from early adolescence into young adulthood: a longitudinal twin study of comorbidity of alcohol, tobacco and illicit drug use. Addiction, which has been published in final form at http://dx.doi.org/10.1111/add.14076. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.

Etiological influences on continuity and co‐occurrence of eating disorders symptoms across adolescence and emerging adulthood

Objective: The role of common and symptom‐specific genetic and environmental influences in maintaining eating disorder symptoms across development remains unclear. This study investigates the continuity and change of etiological influences on drive for thinness, bulimia, and body dissatisfaction symptoms and their co‐occurrence, across adolescence and emerging adulthood. Method: In total, 2,629 adolescent twins (mean age = 15.20, SD = 1.95) reported eating disorders symptoms across three waves of data collection. Biometric common pathways model was fitted to estimate genetic and environmental contributions to the continuity of each symptom over time, as well as time‐ and symptom‐specific influences. Results: Drive for thinness and body dissatisfaction symptoms showed a pattern of high continuity across development and high correlations with each other, whereas bulimia symptoms were moderately stable and less associated with the other two symptoms. Latent factors reflecting continuity of each symptom were largely under genetic influence (Al = 0.60–0.82). New genetic influences contributing to change in the developmental course of symptoms were observed in emerging adulthood. Genetic influences correlated considerably between the three symptoms. Non‐shared environmental influences were largely time‐and symptom‐specific, but some contributed moderately to the continuity across development (El = 0.18–0.40). The etiological overlap was larger between drive for thinness and body dissatisfaction symptoms than with bulimia symptoms. Discussion: The results provide preliminary evidence that stable as well as newly emerging genetic influences contribute to the co‐occurrence of drive for thinness, bulimia, and body dissatisfaction symptoms across adolescence and emerging adulthood. Conversely, environmental influences were less stable and contributed to change in symptoms over time

The role of sense of coherence and loneliness in borderline personality disorder traits: a longitudinal twin study

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

The relationship between life events and sense of coherence in adolescence. A longitudinal twin study

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

Making high-quality measures available in diverse contexts — The psychometric properties of the Revised Child Anxiety and Depression Scale in a Norwegian sample

Objectives - Recent initiatives have recommended the Revised Child Anxiety and Depression Scale (RCADS) for use in research and as patient-reported outcome in health care globally. We aimed to investigate, for the first time, whether the psychometric properties of the anxiety and depression youth self-report measures, RCADS-47 and RCADS-25, generalize to a Norwegian setting. Methods - We examined gender and age differences in symptomatology among 592 children (mean age 10.7 years), and conducted a psychometric investigation of the internal reliability, structural validity, measurement invariance and convergent validity of the RCADS-47 and RCADS-25 youth versions. Results - Girls reported higher levels of anxious and depressive symptoms than boys, but no age differences were observed. Reliability coefficients for the RCADS-47 and RCADS-25 scales indicated good internal consistency. Structural validity for RCADS-47 and RCADS-25 was supported by confirmatory factor analyses results. For both measures, strong gender-based measurement invariance was present. Convergent validity of the RCADS-47 and RCADS-25 with other well-established self-report measures for anxiety (Multidimensional Anxiety Scale for Children) and depression (The Short Mood and Feelings Questionnaire) was supported. Conclusion - The RCADS-47 and RCADS-25 youth versions are valid and reliable instruments for measuring symptoms of anxiety and depression in a Norwegian setting. The results add to the evidence supporting RCADS's cross-cultural validity