Alcohol and cannabis motives: differences in daily motive endorsement on alcohol, cannabis, and alcohol/cannabis co-use days in a cannabis-using sample

Objective: Same day use of alcohol and cannabis is prevalent among emerging/young adults and increases the risk for negative consequences. Although motives for alcohol and cannabis use are well-documented, specific motives on co-use days are under-investigated. We examined differences in motives on single substance use (i.e. alcohol or cannabis) versus co-use days in a sample of primarily cannabis-using emerging/young adults. Methods: Participants (N = 97) aged 18–25 (M_age = 22.2) were recruited from an urban Emergency Department (55.7% female, 46.4% African American, 57.7% public assistance) for a prospective daily diary study about risk behaviors. Participants received prompts for 28 daily text message assessments (up to 2716 surveys possible) of substance use and motives (social, enhancement, coping, conformity). We divided use days into three groups: alcohol use only (n = 126), cannabis use only (n = 805), and co-use (n = 237). Using fixed effects regression modeling, we fit models to estimate within-person effects of alcohol and cannabis motives on day type (alcohol/cannabis co-use versus single use). Results: In adjusted models, greater cannabis-related enhancement and social motives were associated with increased likelihood of co-use days compared to cannabis-only days. In contrast, greater alcohol-related social motives were associated with co-use days versus alcohol-only days in unadjusted, but not in adjusted models. Conclusions: Findings suggest that cannabis use motives associated with increasing positive affect may be most compelling for those engaging in alcohol/cannabis use on a given day. Intervention programs for alcohol/cannabis use should address alcohol and cannabis use motives in relation to increasing positive affect and engaging in social situations.