effect of the ALDH2 protective allele (Irons et al., 2012). For the ADH1B rs1229984 variant, Hasin et al. (2002) observed a weaker protective role in certain groups, which was hypothesized to reflect differences in environmental exposure to heavy drinking. Our findings expand on these earlier observations by demonstrating that the critical high-risk social context of adolescent peer drinking is associated with the loss of the protective genetic effect of the ADH1B variant in European and African Americans.
