Alcohol and Cannabis Cross Motives, Class Analysis, and Substance Use among Concurrent Users.

Background: Substance use motives refer to an individual's reasons for engaging in substance use. Although the respective alcohol and cannabis literatures have linked specific substance-use motives to indices of use, less is known about motives in concurrent users, particularly examination of cross-motives (e.g., cannabis motives predicting alcohol use). Methods: The present work examined motives for use in a sample of concurrent users to assess relations between motives and alcohol and cannabis outcomes (quantity, frequency, and use disorder symptoms) using both variable- and person-centered approaches. Finally, the present work aimed to discern the impact of timeframe selection for defining concurrent use (i.e., past year, past two weeks). Participants (N = 524) consisted of individuals that endorsed having used both alcohol and cannabis in the past year with subsample (N = 192) of individuals endorsing past two-week concurrent use. Results: Univariate linear regression analyses revealed small to medium positive relations between all alcohol motives and alcohol outcomes and small to medium positive relations between cannabis social, coping, enhancement, and expansion motives and cannabis use. Regressions examining cross-motives and multivariate models revealed wide variability in relations. Mixture analyses revealed a three-class solution (i.e., High Motives, Positive Alcohol, and Low Conformity) for past year concurrent users and a two-class solution (i.e., Low Motives and High Motives) for past two-week concurrent users. Discussion: Examination of motive classes revealed differences in substance, particularly cannabis, outcomes as a function of class membership. Findings are useful in classifying concurrent users' motives and highlight the importance of timeframe selection.