Causality and Pleiotropy in the Association Between Bullying Victimization in Adolescence and Depressive Episodes in Adulthood

Gene-Environment Interplay Linking Peer Victimization With Adolescents' Trajectories of Depressive Symptoms

OBJECTIVE

This study examined to what extent genetic and environmental factors explain-either additively or interactively with peer victimization-different trajectories of adolescents' depressive symptoms and whether genetic factors related to distinct trajectories are correlated with peer victimization.

METHOD

Participants included 902 twins (52% girls) who self-reported peer victimization and depressive symptoms in grades 6, 7, 8, 9, and 11.

RESULTS

Growth mixture modeling revealed 3 trajectories of depressive symptoms: low (69.2% of participants), increasing (19.5%), and high-decreasing-increasing (11.3%). Biometric modeling showed that, for both sexes, genetic factors explained roughly half (52.6%, 47.5%) of the probability of following either a low or an increasing trajectory. Genetic influences (41%) were also observed for the high-decreasing-increasing trajectory, albeit only for girls. Nonshared environmental influences explained the remaining variances, along with shared environmental influences (27%) on the high-decreasing-increasing trajectory. Only for the low and the increasing trajectories, nonshared environmental influences increased with more frequent peer victimization (b_low = 0.206, 95% CI [0.094, 0.325]; b_increasing = 0.246, 95% CI [0.143, 0.356]). Moreover, peer victimization was associated with a lower probability of a low trajectory and a higher probability of an increasing or high-decreasing-increasing trajectory, and these associations were mostly explained by common underlying genetic factors.

CONCLUSION

Youth expressing (partly inherited) depressive symptoms may be at risk of peer victimization. However, increasing depressive symptoms in victims may be mitigated by other environmental factors except for those who enter adolescence with already high levels of depressive symptoms.

Prospectively Predicting Adult Depressive Symptoms from Adolescent Peer Dysfunction: a Sibling Comparison Study

Previous studies have shown that peer dysfunction in adolescence predicts depression in adulthood, even when controlling for certain individual- and/or family-level characteristics. However, these studies have not controlled for numerous potential familial confounders, precluding causal inferences. The present study therefore used a sibling comparison design (i.e., comparing siblings within families) to test whether peer dysfunction (e.g., lack of friendships, victimization) in adolescence continues to predict depression in adulthood after accounting for unmeasured familial confounds and individual characteristics in adolescence. Participants’ (N = 85) dysfunction with peers was assessed in adolescence (M_age = 13.21, SD = 3.47) by self- and parent-report, and adult depressive symptoms were assessed up to five times, up to 38 years later. Multilevel modeling was used to examine the effect of adolescent peer dysfunction on adult depressive symptoms after adjusting for familial confounds and/or individual characteristics in adolescence (e.g., baseline depressive symptoms, dysfunctional relations with siblings/parents). Both self-reported (b = 1.28, p < 0.001) and parent-reported (b = 0.56, p = 0.032) adolescent peer dysfunction were associated with greater depressive symptom severity in adulthood in unadjusted models. Self-reported (but not parent-reported) adolescent peer dysfunction continued to predict adult depressive symptoms after controlling for familial confounding and measured covariates such as adolescent depressive symptoms and relations with siblings and parents (b = 1.06, p = 0.035). Although confidence intervals were wide and the potentially confounding effects of numerous individual-level factors were not ruled out, these findings provide preliminary evidence that perceived peer dysfunction in adolescence may be an unconfounded risk factor for depressive symptoms in adulthood.

Links between peer victimization, dating violence victimization and depression in adolescence: A genetically-informed study

OBJECTIVE

The current study aimed to test if individuals with inherent dispositions to depression-related cognitions and behaviors are more at risk of experiencing relational difficulties, such as peer victimization and dating violence victimization.

METHOD

This study used a genetically informed design with 806 twins (51.5% girls) to test 1) if at least part of the association between peer victimization in school and dating violence victimization in emerging adulthood can be explained by common underlying heritable factors. Participants provided repeated assessments of their peer victimization in school at ages 13 through 17, their depression symptoms at ages 13 through 19, as well as their victimization in dating relationships at age 19.

RESULTS

A Cholesky decomposition based on structural equation modeling supported the hypotheses. Specifically, the association between peer victimization and dating violence victimization was to a significant extent explained by common underlying genetic vulnerabilities that were associated with depression symptoms. No sex moderation was found.

CONCLUSIONS

The findings highlight the importance of addressing early indicators of vulnerability toward depression symptoms to prevent victimization by peers or dating partners.

Violent Victimization, Stressful Events, and Depression: A Longitudinal Study of Young Adults in the U.S

We surveyed a sample of young adults in the United States to determine (1) whether/how depression is affected by violent victimization during childhood and/or by recent stressful events, as well as (2) whether any observed links between depression and violent victimization and/or stressful events would be uniform across racial/ethnic groups. Using data from the National Longitudinal Survey of Youth 1997 cohort, we measured respondent depression in 5 interview waves dating 2004-2015. Our final sample for analysis numbered 22,549 person-waves. Our study showed that violent victimization in childhood, and recent stressful events, as well, alike exacerbated depression. Moreover, as we analyzed, in turn, the data for each ethnic subsample, we observed differential patterns in depression's associations with victimization. Childhood violent victimization-and also recently encountered stress-has a significant role in the development of depression in adulthood; this role appears to be moderated by race/ethnicity.

Genetic and Environmental Influences on Different Forms of Bullying Perpetration, Bullying Victimization, and Their Co-occurrence

Bullying comes in different forms, yet most previous genetically-sensitive studies have not distinguished between them. Given the serious consequences and the high prevalence of bullying, it is remarkable that the aetiology of bullying and its different forms has been under-researched. We present the first study to investigate the genetic architecture of bullying perpetration, bullying victimization, and their co-occurrence for verbal, physical and relational bullying. Primary-school teachers rated 8215 twin children on bullying perpetration and bullying victimization. For each form of bullying, we investigated, through genetic structural equation modelling, the genetic and environmental influences on being a bully, a victim or both. 34% of the children were involved as bully, victim, or both. The correlation between being a bully and being a victim varied from 0.59 (relational) to 0.85 (physical). Heritability was ~ 70% for perpetration and ~ 65% for victimization, similar in girls and boys, yet both were somewhat lower for the relational form. Shared environmental influences were modest and more pronounced among girls. The correlation between being a bully and being a victim was explained mostly by genetic factors for verbal (~ 71%) and especially physical (~ 77%) and mostly by environmental factors for relational perpetration and victimization (~ 60%). Genes play a large role in explaining which children are at high risk of being a victim, bully, or both. For victimization this suggests an evocative gene-environment correlation: some children are at risk of being exposed to bullying, partly due to genetically influenced traits. So, genetic influences make some children more vulnerable to become a bully, victim or both.