Four hypotheses guided our inquiry: First, OXTR variation will moderate the association between intervention status and affiliations with substance-using peers. Second, affiliations with substance-using friends will predict 9th-grade alcohol use. Third, OXTR variation will moderate the impact of affiliations with substance-using friends on adolescents’ own alcohol use. Fourth, OXTR variation will moderate the impact of intervention status on the association between affiliations with substance-using friends and individual adolescents’ own alcohol use.
