The present study provides further evidence on the contribution of GABRA2 genetic variation on the strength of the relation between deviant peer affiliation and externalizing behavior. Furthermore, our results suggest that the influence of GABRA2 genetic variation is on one specific subcomponent of this behavior, namely rule breaking but not aggression. Consistent with study hypotheses, peer delinquency positively predicts externalizing behavior. When externalizing behavior was analyzed separately by its subcomponent parts, there was evidence for a significant effect of GABRA2 as a moderator on rule breaking behaviors, but not on aggression. The association was stronger for adolescents carrying the GG genotype compared to A-carriers. This suggests that adolescents with the GG genotype may be more susceptible to the influence of delinquent peer involvement on externalizing behavior driven by rule breaking but not aggression. Moreover, the regions of significance analysis suggest that the interaction is most consistent with a diathesis-stress model (Zuckermann 1999), which suggests that some individuals are more vulnerable to adverse effects of environmental stressors (e.g., delinquent peers) due to their genetic composition. That is, adolescents with the GG
