Real-world simultaneous alcohol and cannabis use: An ecological study of situational motives and social and physical contexts.

Objective: Given the adverse outcomes associated with simultaneous alcohol and marijuana (SAM) use, understanding factors that give rise to occasions of simultaneous use is critical. This study examines the relationships between situational motives and contexts and three situational outcomes: simultaneous alcohol and marijuana use (SAM) use versus cannabis-only use, number of cannabis uses, and subjective effects.

Method: Past-month SAM users ( = 341; 52% female; 75% White; 10% Latinx/Hispanic; age 18-24) from three U.S. college campuses completed 8 weeks of surveys up to five times a day. Three-level generalized linear mixed-effects models tested the effects of situational motives and social and physical contexts on occasion type (SAM vs. cannabis-only), cannabis use, and subjective effects.

Results: Situational social and enhancement motives were related to greater odds of SAM relative to cannabis-only use; expansion motives were reported more often on cannabis-only occasions. Using with others and at friends' places, being with others consuming cannabis, and being with others who are intoxicated were more likely when combining alcohol with cannabis. Increased number of cannabis uses and subjective effects in a social context were evident only on cannabis-only occasions. Using alone and using at home were greater on cannabis-only occasions and were associated with lower cannabis use and subjective effects.

Conclusions: The combination of alcohol and cannabis use occurs during social situations and when motivated by positive reinforcement but number of cannabis uses is not increased when consuming cannabis with alcohol in social situations. Characterizing the complex interplay of situational factors that contribute to risky use will inform interventions. (PsycInfo Database Record (c) 2021 APA, all rights reserved).