The findings reported here have several limitations. First, studying a specific genetic variant provides limited information on the general genetic underpinnings of complex diseases such as alcohol use disorder (Dick and Kendler, 2012). Nevertheless, examination of specific robust variants provides important insight into underlying biological mechanisms that are not assessed by traditional studies of latent genetic influences. Second, other genetic variants may influence associations between ADH1B rs1229984 and drinking behaviors (Meyers et al., 2013; Toth et al., 2011). Third, self-reported peer drinking was viewed as an environmental risk factor in this study, but research suggests that genetic factors contribute to peer alcohol involvement (Fowler et al., 2007). Gene-environment correlations can arise when an individual's heritable behavior evokes an environmental response (evocative rGE) or when an individual possesses a heritable propensity to select an environment (active rGE). In this study, the ADH1B rs1229984 variant was not associated with self-reported peer drinking, supporting our interpretation that peer drinking acts as an environmental modifier, but other gene-environment correlations may still contribute to the observed effects. Fourth, the temporal ordering of peer drinking and
