Association of Peer Victimization in Childhood and Substance Initiation Time: Evidence from a Twin Study

• In Event: Peers and Risky Behaviors

Abstract

Peer victimization, an adverse event especially prevalent among children and adolescents (Sapouna & Wolke, 2013), can occur in various forms, ranging from direct physical attack to indirect social exclusion. It is further categorized into three forms: physical, verbal, and relational bullying (e.g., Juvonen & Graham, 2014). Peer victimization is robustly associated with many adverse developmental outcomes, such as early initiation of drugs. Despite suggestive findings linking peer victimization to early substance use (e.g., Connell et al., 2017), no study to date has explored genetic and environmental contributions to this relationship. Thus, the present study aimed to examine the etiological overlap between peer victimization in childhood and substance initiation time in adolescence.

In the USC longitudinal study of Risk Factors for Antisocial Behavior, 9-10-year-old twins (548 pairs; 55.31% female, 35.96% Hispanic, 30.82% Caucasian, 15.75% Mixed, 12.33% Black/African, and 5.14% Asian - representative of the greater Los Angeles area) reported bullying victimization on the Child Friendship Questionnaire. Alcohol, cigarette, and marijuana initiation time was calculated based on their self-reported ever use in five waves of data collection: 1 = Initiated before 21 years old; 0 = Never ever used before 21 years old (treated as a binary score where higher level indicated more problematic timing of early substance use).

Logistic regression indicated a tendency that higher verbal victimization (OR=3.80 [.93, 15.56]) predicted alcohol initiation before 21 years of age, controlling for sex and ethnicity. Higher verbal (OR=4.14 [1.22, 14.07]) and physical (OR=3.41 [1.21, 9.60]) victimization predicted cigarette initiation before 21. However, these effects (r’s = .11-.18) were too small to meaningly decompose into genetic and environmental influences. There were no other associations of victimization and marijuana initiation before 21 (r’s < .16).

The best-fitting univariate models suggested: verbal victimization was influenced by genetic and nonshared environmental factors (a2=47% [35%, 58%], e2=53% [42%, 65%]). Physical victimization was influenced by genetic or shared environmental and nonshared environmental factors (a2=31% [17%, 43%], e2=69% [57%, 83%]; or c2=25% [14%, 35%], e2=75% [65%, 86%]), which indicated ambiguous familial influences. Relational victimization was influenced by either genetic or shared environmental and nonshared environmental factors (a2=25% [11%, 38%], e2=75% [62%, 89%]; or c2=20% [9%, 31%], e2=80% [69%, 91%]). Genetic, shared environmental and nonshared environmental factors all contributed to alcohol (a2=48% [25%, 80%], c2=40% [9%, 62%], e2=12% [9%, 18%]), cigarette (a2=58% [39%, 81%], c2=27% [4%, 46%], e2=14% [11%, 19%]), and marijuana initiation time (a2=39% [23%, 61%], c2=44% [22%, 60%], e2=17% [13%, 24%]). No sex differences in variance components were detected for any variables.

In conclusion, adolescents who experienced higher verbal and physical victimization in childhood were more likely to use cigarettes before age 21. And there was a tendency that those who experienced higher verbal victimization in childhood were more likely to initiate alcohol drinking before age 21. Nonshared environmental influences played an important role in all forms of childhood peer victimization, whereas genetic, shared environmental, and nonshared environmental factors all played crucial roles in substance initiation time.

Authors

• Li Yu, Purdue University, West Lafayette
  Presenting Author

• Valerie Knopik, Purdue University, West Lafayette

• Kristine Marceau, Purdue University, West Lafayette

• Laura Baker, University of Southern California