One challenge of studying the influence of the ADH1B rs1229984 variant in populations of European and African ancestry is the low frequency of the protective A allele. Although over 1,500 adolescent drinkers were examined in this analysis, only 98 (6%) carried an A allele (of which 36 reported most/all best friends drinking). Nonetheless, the influence of this variant and the GxE interaction was persistently strong in models of first intoxication and first DSM-5 symptom (Table 2). Secondary ancestry-stratified analyses also demonstrated consistent main and interaction effects in the European American subpopulation (N=1,130) and provided trending evidence of main effects in the African American subpopulation (N=420), where power was limited. These analyses, combined with previous studies supporting the protective role of rs1229984 across ancestry groups as well as the moderating effect of social environments, support our conclusion that this variant is associated with a protective effect for early drinking behaviors in European and African Americans, but this genetic protection may be eliminated by adolescent peer drinking.
