The company you keep: The neglected role of affiliating with delinquent friends in the development of the cannabis-violence link.

A growing body of research suggests a potential role of cannabis use on aggressive behaviors. In literature on adolescents, the lack of consideration of important confounders, such as adolescent's affiliation with delinquent peers, limits the possibility to determine whether there might be a direct or indirect link between cannabis use and aggression. Therefore, we sought to examine the effect of delinquent peers on the association between cannabis use and violence. We re-analyzed data from 850 ninth graders who were followed from mid-adolescence to early adulthood. Generalized Estimations Equations (GEE) were conducted to examine whether affiliation with delinquent peers may mediate the relationship between cannabis use and violence. Cross-Lagged Panel Models were also conducted to estimate the directionality of these relationships over time. We additionally tested whether similar relationships may be identifiable when examining rule-breaking behaviors and/or alcohol use. GEE models revealed that both cannabis use and affiliation with delinquent peers were statistically associated with aggressive behaviors. Cannabis use, alcohol use and delinquent peers also predicted rule-breaking behaviors. More precisely, cross-lagged models showed that affiliation with delinquent peers played a partially mediating role in the cannabis-aggression link, and that similar cross-lagged estimates were observed when examining rule-breaking behaviors instead of aggression. Our results indicate that cannabis use may be associated with aggression as well as rule-breaking behaviors, suggesting a broader effect on conduct problems. More importantly, our study highlights the non-negligible role of affiliating with delinquent peers during adolescence.