The Prospective Effects of Parents’ and Friends’ Approval of Drinking on Simultaneous Alcohol and Marijuana Use during College

Background: Recent reports indicate that simultaneous alcohol and marijuana (SAM) use is a growing health concern among college students. As SAM use consists of both alcohol and marijuana, risk factors associated with either can serve as plausible targets by prevention efforts to reduce SAM use. Objectives: To explore this, the current study investigated the direct and indirect effects of two established risk factors for drinking on SAM use: perceived parental permissiveness toward drinking and friends’ approval toward drinking (injunctive norms). Method: Incoming first-year students (N = 470) reported parental permissiveness, injunctive norms, alcohol use, and SAM use at baseline (T1) and 5 months later (T2). SAM use was assessed again 15 months post-baseline (T3). Path analysis was conducted to examine whether T2 variables mediated relationships between T1 variables and T3 SAM use. Results: Results revealed that T2 student alcohol use mediated the effects of T1 parental permissiveness, injunctive norms, and alcohol use on T3 SAM use. Conclusions/Importance: Findings from this study extend research on SAM use by identifying perceived parental permissiveness and injunctive drinking norms as risk factors for SAM use through their effects on alcohol use. Based on these findings, it is plausible that parent-based interventions and interventions targeting peer injunctive norms during the first year of college could be used to effectively prevent or reduce SAM use.