Few other studies have controlled for genetic/environmental correlation while examining causal processes between self and peer alcohol use phenotypes. Nevertheless, previous research has identified genetic influences on peer substance use (Agrawal et al., 2010; Dick et al., 2007); there is support for rGE in the context of peer and self substance use (Fowler et al., 2007; Loehlin, 2010; Wills and Carey, 2013); and others have utilized genetically informative samples when exploring the relationship between peer and self alcohol use (Poelen et al., 2007; Scholte et al., 2008) without explicitly modeling selection and influence. Our results are also consistent with previous studies that have found that the relative impact of social influence is mitigated once selection processes are accounted for (Jaccard et al., 2005; Poelen et al., 2007), though in the current study those influences remain statistically significant. Evidence from additional genetically informative samples is needed to determine the extent to which genetic/environmental correlation, social selection, and social influence contribute to the phenotypic association between individual and peer substance use.
