Reconciling multiple sources of influence: Longitudinal associations among perceived parent, closest friend, and popular peer injunctive norms and adolescent substance use.

Prospective associations over a 5-year period were examined among perceived parent, closest friend, and popular peer injunctive norms and the onset and frequency of adolescent substance use within a diverse (53% female, 45.5% White non-Hispanic, 22.3% Hispanic, 21.5% Black, 1% Asian, and 6.4% another race) sample of 868 seventh- and eighth-grade adolescents from 2012 to 2017. Analyses revealed adolescents' substance use norms were more lenient than perceptions of their parents' and stricter than perceptions of their closest friends'. Stricter perceptions of parent and closest friend norms, but not popular peer norms, were significantly associated with a later onset of alcohol, marijuana, and cigarette use, and the magnitude of the effect of each source' on later substance use varied across development.