Unplanned versus planned simultaneous alcohol and marijuana use in relation to substance use and consequences: Results from a longitudinal daily study.

Objective: The current study expands the literature on simultaneous alcohol and marijuana (SAM) use by focusing on the distinction between unplanned and planned SAM use to identify potential intervention targets. This study explored whether unplanned or planned SAM use was associated with differences in alcohol and/or marijuana use and consequences. Method: A community sample of young adults (aged 18-25) with recent alcohol and SAM use was recruited [N = 409; mean (SD) = 21.61 (2.17) years; 50.9% female; 48.2% non-Hispanic/Latinx White]. Participants completed five 2-week bursts of online daily surveys (2 ×/day; 81.99% of morning and 82.23% of afternoon surveys completed) and reported on substance use intentions and behavior. Results: Descriptive findings showed that among days on which participants reported SAM use, 41.85% of the days were unplanned SAM use days. Based on daily-level results from multilevel models, on days with unplanned SAM use, young adults reported consuming fewer drinks, fewer hours high from marijuana, and lower subjective intoxication/high, compared to planned SAM use days, thus indicating that planned SAM use was riskier. Unplanned SAM use was not significantly associated with positive or negative consequences related to alcohol or marijuana, after accounting for the number of drinks or hours high from marijuana. Conclusions: Current findings suggest that interventions should target days on which young adults are planning to engage in SAM use. Future work is needed to identify factors that predict planned SAM use on specific occasions and also to disentangle the potential role of unplanned heavy use. (PsycInfo Database Record (c) 2021 APA, all rights reserved).