Alcohol and cannabis co-use in a national sample of US adults ages 30-80

Introduction: Growing cannabis legalization has coincided with an increased focus on use of both alcohol and cannabis (AC co-use) among younger people; however, little is known about AC co-use among adults over age 30. This study examines the prevalence of different types of AC co-use among adults, as well as compares AC co-users and alcohol-only users on individual, social network, and neighborhood characteristics.Methods: Data come from three annual surveys of a nationally representative sample of 1,770 U.S. adults, initially between the ages of 30-80, conducted between 2019 and 2021. The baseline sample is 52.8 years old on average, 51.8 % female, and 60.1 % non-Hispanic White.Results: Past month co-use at baseline was reported by 8.4% of adults, and mostly consisted of simultaneous use, with less than 5% of the sample initiating co-use over the two-year follow-up period. Multivariable models indicate AC co-use was cross-sectionally associated with respondents being male, younger, Hispanic (vs White), and having more alcohol use and related problems, and with their social network composition (e.g., having more drinking buddies and cannabis users in the network). However, co-use status was not associated with mental health, physical ailments, or neighborhood quality. Longitudinal analyses indicated that AC co-use at baseline predicted more alcohol use one year later and alcohol related problems two years later among men only.Conclusions: AC co-use among adults over age 30 deserves further attention given its prevalence and associations with heavier drinking and related problems. Network-focused interventions may be a promising approach for reducing AC co-use.