Associations between alcohol and cannabis use order, frequency, quantity, and consequences in a college sample of individuals who co-use alcohol and cannabis

Background and objectives: Using both alcohol and cannabis (either at the same time or at different times) is common among college students, and is called "co-use." Using these substances simultaneously, such that their effects overlap, is thought to be an especially risky co-use pattern. Gaining a better understanding of how co-use patterns relate to substance use and consequences could aid prevention and intervention efforts.

Methods: We examined college students (N = 401) who reported using both alcohol and cannabis at least once in the past 30 days. Path analysis was used to explore relations among co-use patterns (number of days in a typical week that participants used both alcohol and cannabis; the number of days using alcohol first, cannabis first, alcohol last, and cannabis last; the number of days of simultaneous use), past-30-day alcohol and cannabis consequences, use frequency, and typical quantities used.

Results: Each additional day of using alcohol first was associated with fewer past-30-day cannabis consequences. Each additional day of using cannabis first was associated with fewer alcohol-related consequences. Each additional day of using alcohol and cannabis on the same day and each additional day of simultaneous use were both associated with less cannabis used and alcohol consumed in a typical week.

Conclusions and scientific significance: This study is among the first to identify associations between alcohol and cannabis order and outcomes (i.e., consequences and consumption). Results suggest that modifying which substance is used first on a given day could be a practical intervention strategy for individuals who co-use alcohol and cannabis.