The socio-environmental context of simultaneous alcohol and marijuana use among young adults: Examining day-level associations

Introduction and Aims Simultaneous alcohol and marijuana (SAM) use is reported by roughly 30% of young adult drinkers. Among SAM users, SAM use days have more negative substance-related consequences than single-substance days. Little information is available about contextual factors contributing to the likelihood of SAM use on a particular day. This study compared days on which individuals reported SAM use relative to days on which they reported alcohol but not marijuana use in terms of physical location, engagement in risky activities and social context of use. Design and Methods Participants were 148 young adults (57% female) reporting past-month SAM use and past two-week binge drinking. Participants completed up to 14 daily surveys assessing substance use behaviour and socio-environmental characteristics of use. Results For those <21 years, only using at home was associated with greater odds of SAM use. For those 21+, using at a friend's house and outdoors were associated with increased odds of use; using at a bar/club was associated with lower odds. Using alone was associated with lower odds of use for those 21+. Engagement in risky activities (pre-gaming and drinking games) was not associated with SAM use. Discussion and Conclusions SAM days are linked with use in private settings and social situations. Despite experiencing more harms on SAM days, SAM use is not more likely than alcohol use alone to occur in certain environments and situations traditionally found to be linked with increased risk. Findings may provide key insight for developing context-informed interventions focused on SAM use.