Although findings that link peer affiliations to genetic variation, like all biometric results, do not address which genes, or how such genes, are involved, they demonstrate the viability of an approach that hypothesizes about specific genetic variants, such as those related to oxytocin, that might contribute to affiliations with substance-using peers. The viability of a potential role for specific genes as contributors to risky peer affiliations and their impact on drinking is further buttressed by recent candidate gene findings. For example, Griffin et al. (2015) found that carriers of at least one copy of the DRD4 7-repeat allele (7+) reported a stronger positive association between perceived peer pressure and increased alcohol use than non-carriers. Similarly, in a randomized experiment, Larsen et al. (2010) found that when exposed to heavy-drinking confederates, young adults carrying DRD4 7+ drank more than those without the allele. A second randomized study suggested a mechanism behind this interaction: Creswell et al. (2012) found that DRD4 7+ carriers were more sensitive to the social bonding effect of alcohol than 7- individuals.
