Personality Maturation during the Transition to Working Life: Associations with Commitment as A Possible Indicator of Social Investment

The social investment theory (SIT) proposes that personality maturation is triggered by transitions into age–graded roles and psychological commitment to these roles. The present study examines the predictions of SIT by focusing on the transition from student life to working life. We analysed three–wave longitudinal data and compared participants who made the transition into working life ( N = 226), participants who combined education with work ( N = 387), and participants who did not make the transition at all ( N = 287). In contrast to the predictions of SIT, we found no differences in personality maturation between individuals who made the transition into working life and those who did this only partly or not at all. Psychological commitment to work did not explain individual differences in personality maturation for those who made the transition (partly) into working life after controlling for multiple testing. Therefore, the present study did not support the predictions of SIT. © 2019 The Authors European Journal of Personality published by John Wiley & Sons Ltd on behalf of European Association of Personality Psychology

Positive Daily Experiences Are Associated with Personality Trait Changes in Middle–Aged Mothers

Theory and research have suggested that recurrent daily experiences can affect personality traits. The present study examined the longitudinal relation between individual differences in positive daily experiences and the Big Five personality traits. Data came from Dutch mothers ( N = 483; M age = 44 years at T1) who completed up to six yearly personality questionnaires and 15 between–year assessment bursts, lasting five consecutive days each. Using multilevel structural equation modelling, we found that individual differences in daily experiences of positive affect and perceived relationship support/affection with partners and children were positively associated with subsequent rank–order changes in all Big Five personality traits. In contrast, we found little evidence that personality traits were associated with rank–order changes in daily experiences, which may be due to the very–high rank–order stability of positive affect and relationship support. Furthermore, positive daily experiences demonstrated incremental validity in predicting rank–order changes in trait agreeableness, emotional stability, and openness, over and above daily negative affect and relationship conflict. The results suggest that positive affective and interpersonal daily experiences contribute to positive personality trait changes in middle adulthood. We discuss these results in the context of contemporary theories of personality trait development. © 2018 European Association of Personality Psychology

Genome-wide association meta-analysis of age at first cannabis use

BACKGROUND AND AIMS

Cannabis is one of the most commonly used substances among adolescents and young adults. Earlier age at cannabis initiation is linked to adverse life outcomes, including multi-substance use and dependence. This study estimated the heritability of age at first cannabis use and identified associations with genetic variants.

METHODS

A twin-based heritability analysis using 8055 twins from three cohorts was performed. We then carried out a genome-wide association meta-analysis of age at first cannabis use in a discovery sample of 24 953 individuals from nine European, North American and Australian cohorts, and a replication sample of 3735 individuals.

RESULTS

The twin-based heritability for age at first cannabis use was 38% [95% confidence interval (CI) = 19-60%]. Shared and unique environmental factors explained 39% (95% CI = 20-56%) and 22% (95% CI = 16-29%). The genome-wide association meta-analysis identified five single nucleotide polymorphisms (SNPs) on chromosome 16 within the calcium-transporting ATPase gene (ATP2C2) at P < 5E-08. All five SNPs are in high linkage disequilibrium (LD) (r2  > 0.8), with the strongest association at the intronic variant rs1574587 (P = 4.09E-09). Gene-based tests of association identified the ATP2C2 gene on 16q24.1 (P = 1.33e-06). Although the five SNPs and ATP2C2 did not replicate, ATP2C2 has been associated with cocaine dependence in a previous study. ATP2B2, which is a member of the same calcium signalling pathway, has been associated previously with opioid dependence. SNP-based heritability for age at first cannabis use was non-significant.

CONCLUSION

Age at cannabis initiation appears to be moderately heritable in western countries, and individual differences in onset can be explained by separate but correlated genetic liabilities. The significant association between age of initiation and ATP2C2 is consistent with the role of calcium signalling mechanisms in substance use disorders.

Person–Group Dissimilarity in Personality and Peer Victimization

The present study examined the role of person–group dissimilarity in personality in peer victimization. It was hypothesized that adolescents who show more deviation from the classroom norm in personality experience more peer victimization. Data from 1108 adolescents (48% boys; Mage = 13.56 years, SD = 1.13) from 54 classrooms were used to test this hypothesis. Data included measurements of self–reported and bully–disclosed victimization and Big Five and Dark Triad personality traits. Results of generalized linear mixed models including polynomial equations and subsequent response surface analyses partly supported our hypothesis. Person–group dissimilarity in the shape of personality profiles was related to more bully–disclosed victimization, but not to self–reported victimization. Dissimilarity in neuroticism and Machiavellianism was related to both more self–reported and bully–disclosed victimization. Dissimilarity in extraversion, openness to experience, and psychopathy was only related to more self–reported victimization. Unexpectedly, dissimilarity in agreeableness was related to less self–reported victimization. Moreover, our results also indicated that certain levels of congruent person–group combinations in agreeableness, neuroticism, Machiavellianism, and psychopathy were related to more peer victimization. Overall, findings of this study emphasize the importance of considering classroom norms in relation to peer victimization. Copyright © 2017 European Association of Personality Psychology

Testosterone and cortisol in relation to aggression in a non-clinical sample of boys and girls

Testosterone and cortisol have been proposed to jointly regulate aggressive behavior. However, few empirical studies actually investigated this joint relation in humans, and reported inconsistent findings. Also, samples in these studies were small and/or specific, and consisted largely of males. Therefore, in the current study testosterone and cortisol in relation to aggression were investigated in a non-clinical sample of 259 boys and girls (mean age 16.98 years, SD = 0.42, 56% boys). A positive testosterone/cortisol ratio, that is, high testosterone relative to cortisol, was found to be associated with aggressive behavior, explaining 7% of the variance. The interaction between testosterone and cortisol was not related to aggressive behavior and gender differences were not found. The ratio may reflect an imbalance leaving the individual more prone to rewarding aspects, than fearful of negative implications of aggressive behavior. Current findings indicate that this relation can be generalized to aggression in non-clinical adolescents.

Autonomy, attachment and psychosocial adjustment during adolescence: a double-edged sword?

Both autonomy and attachment are positively related to psychosocial adjustment during adolescence. The aim of the present study was to examine the assumption that a high level of autonomy within a context of attachment provides the best constellation for psychosocial adjustment. Subjects were 400 adolescents. Attitudinal, emotional and functional autonomy were connected with attachment to father, mother and peers to predict indices of psychosocial adjustment: social competence, academic competence, self-esteem, problem behaviour and depressive mood. Only main effects of autonomy and attachment were found. There was no evidence for an extra positive effect of being both autonomous and strongly attached.