Adolescent Substance Use and Aggressive Behaviours in Multiple Structural Peer Contexts (CAS)

Many changes in health-related behaviours occur during adolescence (Williams, Holmbeck, & Greenley, 2002). Peers play a critical role in such behaviour changes, since they can substantially influence youths’ health behaviours (Ryan, 2001). Adolescents tend to adhere to the behavioural norms (i.e., peer context’s average engagement in behaviour) conveyed by peers in relevant peer contexts as this will likely enhance their status, which is of increasing concern to adolescents (Brown & Larson, 2009). As such, adolescents tend to be similar in behaviour to their peers (homophily; Lazarsfeld & Merton, 1954). Since adolescents interact with peers in multiple contexts, adolescent are exposed to multiple, potentially opposing behavioural norms. Therefore, various peer contexts may account for behavioural similarity (Kiesner, Kerr, & Stattin, 2004) and behavioural similarity may vary across different peer contexts as a function of the specific behaviour. The current study examined homophily effects of three structural peer contexts (classroom, school, age-cohort) on adolescent substance use (tobacco, alcohol, cannabis) and aggressive behaviours (bullying, physical fights) in a sample of 5.642 12- to 16-year-old Dutch adolescents (264 classes, 68 schools) drawn from the 2009/2010 HBSC study. Multilevel analyses revealed significant homophily effects of age-cohort and classroom norm on individual substance use. Cannabis use, however, was related to school norm and not classroom norm. Furthermore, age-cohort’s effect on alcohol use was moderated by classroom norm; low classroom alcohol use weakened the effect of high age-cohort alcohol use. Aggressive behaviours were significantly predicted by classroom and school norms. To conclude, substance use appears to be a more age-related phenomenon, where aggressive behaviours appear to be more affected by direct interactions (classmates) or shared environments (schoolmates). Similarly, shared environments may also play an important role in cannabis use. These results help policy makers to determine which peer context to target first to promote adolescent health.