In addition to these main effects, twin studies have also demonstrated interdependent effects between genetic and environmental influences on externalizing behavior, indicating that adolescents with different genetic predispositions may be differentially susceptible to peer influences. Affiliation with delinquent peers has been shown to moderate genetic influences on adolescent conduct problems, with genetic effects accounting for more of the variance in problem behavior as individuals are exposed to higher levels of peer antisocial behavior (Button et al., 2007). Similar evidence has emerged from studies focused on narrower dimensions of adolescent problem behavior. With respect to adolescent alcohol use, for example, as the total number of peers who drink increased, so too did the degree to which additive genetic factors accounted for variability in the frequency with which adolescents drink (Dick et al., 2007c). Likewise, findings suggest that while affiliating with aggressive peers generally increases risk for aggression among kindergarten aged children, it can be particularly detrimental for those who are also genetically predisposed (van Lier et al., 2007). Together, these studies suggest that minimizing exposure to peer antisocial behavior may serve
