Dyadic cannabis use, alcohol use and relationship satisfaction: A daily diary study.

Objective: Intimate relationships are important contexts for understanding individuals' substance use patterns and trajectories. Using a dyadic daily diary design reporting over 14 consecutive days, the present study examined the association between cannabis use, alcohol use, and momentary relationship satisfaction among adult couples METHOD: Eligible individuals on Prolific were invited to participate. We identified 33 couples where both partners participated. Participants completed a baseline survey and a 14-day daily diary study assessing their daily cannabis use, alcohol use, and relationship satisfaction. Multilevel modeling was used, within an Actor-Partner Interdependence Model (APIM), to evaluate the individual and interactive effects of one's own use and their partner's use on relationship satisfaction RESULTS: Significant actor and partner effects of alcohol and cannabis use were found using both baseline and daily report data. For individuals who use cannabis more heavily among sampled couples, cannabis and alcohol co-use was associated with reduction in their own next-day relationship satisfaction while alcohol-only use was significantly associated with increased next-day satisfaction. There were no significant effects of one's own or their partner's effects for individuals who use cannabis more lightly.

Conclusions: Findings replicate and extend prior research by demonstrating the dynamic nature of dyadic substance use and highlighting the unique impact of alcohol and cannabis co-use on daily relationship functioning.