Abstract
BACKGROUND: Prior research shows that negative drinking outcomes among young adults may be exacerbated by cannabis use. However, to date, there have been few longitudinal studies of associations between cannabis use and negative alcohol-related consequences. This study examined longitudinal within-person associations between cannabis use and several domains of negative alcohol consequences among young adults and explored the moderating role of sex. METHOD: We analyzed data from N = 997 students assessed 4 times per year over the first 3 years of university. At each time point, participants completed measures of past-month cannabis use frequency, typical weekly number of drinks, and 8 domains of negative alcohol consequences. Longitudinal associations were examined in multilevel models. RESULTS: Within-person changes in frequency of cannabis use were not uniquely associated with changes in total alcohol consequences aggregated across several alcohol consequence domains. However, when examining alcohol consequence domains separately, within-person increases in cannabis use frequency were specifically associated with increases in some (but not all) of the more severe types of alcohol consequences, including risky behaviors, poor self-care, and alcohol dependence symptoms. No support was observed for the moderating role of sex in the longitudinal within-person associations between cannabis use and alcohol consequence domains. CONCLUSIONS: Findings suggest that within-person changes in cannabis use frequency among young adults are associated with corresponding changes in some domains of alcohol consequences (but not others) when examined over the course of several years. Results may inform targeted harm reduction interventions for young adult drinkers who use cannabis, although future research is needed to clarify the mechanisms of the observed associations.