Day-level latent classes of alcohol and cannabis use motives: Associations by combined use, level of use, and consequences.

OBJECTIVE: Motives for alcohol and cannabis use are highly dynamic and vary across days. Limited prior work has explored endorsement of multiple motives within a day and how select combinations correspond to use patterns among young adults. The present study used a nuanced analytic technique-multilevel latent class analysis-applied to day-level data to characterize motives for alcohol and cannabis use and examine the associations between day-level class membership and same-day alcohol, cannabis, and co-use outcomes. METHOD: = 1.31]; 51.5% female; 75% White) were college students enrolled in a 54-day ecological momentary assessment study, yielding 5,907 daily reports. Each day, participants recorded their motives for using alcohol and/or cannabis as well as their substance use behavior (type and level of use, substance-related consequences). RESULTS: Six day-level classes were identified using multilevel latent class analysis: fun motives days (37.5% of days), social and fun motives days (36.4%), offered/availability motives days (10.1%), expand and fun motives days (9.0%), coping motives days (5.0%), and general high motives days (2.0%). Classes differed across all substance use outcomes and harms. General high motives days had the highest proportion of co-use days and the greatest level of alcohol use, negative consequences, and cannabis use occasions, followed by the social and fun motives class. CONCLUSIONS: Most alcohol and/or cannabis use days were characterized by multiple motives, with the greatest level of substance use and harms associated with days in which multiple motives were endorsed. Findings may help inform just-in-time interventions aimed at reducing substance use and co-use-related consequences. (PsycInfo Database Record (c) 2026 APA, all rights reserved).