Alcohol and marijuana use in early adulthood for at-risk men: Time-varying associations with peer and partner substance use

Outcome-specific substance use of peers and partners was significantly associated with indicators of alcohol and marijuana use in men's early adulthood, with robust effects of peer substance use through age 30 years and with time spent with peers influencing alcohol use. Time with partner was protective against marijuana use unless the partner used marijuana. Peers and partners should be considered in intervention efforts to effectively reduce men's substance use in early adulthood.