Early-day psychosocial predictors of later-day simultaneous alcohol and cannabis use among college-attending young adults.

OBJECTIVE: Simultaneous use of alcohol and cannabis is prevalent among young adults and associated with heightened risk for harms. Individuals who engage in simultaneous use report a variety of types of use occasions and risk factors driving use occasions are unique and dynamic in nature. Intervention content may thus need to adapt to address differences across occasions. As a first step toward developing momentary interventions, it is critical to identify whether and when psychosocial factors are associated with simultaneous use. The present study aimed to identify the most critical morning and afternoon risk factors for later-day simultaneous use.

METHOD: Participants were 119 young adult college students (63% female; 73% non-Hispanic/Latinx White) who reported weekly simultaneous use at baseline. Participants completed an online baseline survey and an ecological momentary assessment protocol (eight prompts/day) across four consecutive weekends.

RESULTS: Multilevel models revealed that morning willingness to engage in simultaneous use and social motives were associated with higher odds of later-day simultaneous use. Afternoon willingness and cross-fading motives were significantly associated with higher odds of later-day use. Morning and afternoon conformity motives were associated with lower odds of use.

CONCLUSIONS: Early-day willingness to use, morning social motives, and afternoon cross-fading motives were the most salient predictors of later-day simultaneous use and may serve as viable tailoring variables to incorporate in momentary interventions. As simultaneous use episodes commonly start after 9 p.m., there is a large time window in between early-day predictors and use behavior during which timely intervention content could be delivered. (PsycInfo Database Record (c) 2025 APA, all rights reserved).