Descriptive norms for simultaneous cannabis and alcohol use predict simultaneous use patterns assessed via daily surveys.

Objective: Simultaneous cannabis and alcohol use is common, but few studies have examined normative perceptions of simultaneous use. This study examined unique associations of baseline descriptive norms for simultaneous use (i.e., perceptions about others' simultaneous use) with simultaneous use behaviors assessed via daily surveys.

Method: Young adults reporting frequent simultaneous use ( = 150) completed baseline measures of descriptive norms for the frequency of simultaneous use and the amounts of cannabis and alcohol consumed during typical simultaneous use occasions. Further, participants completed measures of descriptive norms for the frequency and quantity of cannabis and alcohol use in general (not limited to simultaneous use). Norms were assessed referencing both peer and friend groups. Following this assessment, participants completed 21 daily smartphone surveys assessing cannabis and alcohol use each day. Simultaneous use was operationalized as same-day use of cannabis and alcohol.

Results: Multilevel models revealed that, controlling for descriptive norms for cannabis and alcohol use in general, perceiving more frequent simultaneous use among friends (but not peers) was significantly associated with a greater tendency to engage in simultaneous use relative to cannabis-only use across days. Further, perceiving heavier cannabis and alcohol consumption during simultaneous use occasions among friends (but not peers) was significantly associated with greater quantities of cannabis and alcohol consumed, respectively, across simultaneous use days.

Conclusions: Descriptive norms for simultaneous use contribute uniquely to simultaneous use behavior, over and above norms for cannabis use and alcohol use in general. Findings may inform norms-based interventions for young adults who engage in simultaneous use. (PsycInfo Database Record (c) 2025 APA, all rights reserved).