Recreational Marijuana Legalization, Local Retail Availability, and Alcohol and Marijuana Use and Co-Use Among California High School Students.

Abstract

This study examined whether recreational marijuana legalization (RML) and local retail availability were associated with marijuana and alcohol use and co-use among adolescents. We investigated associations between RML and past-30-day marijuana and alcohol use and co-use, and moderating effects of retail availability of marijuana and alcohol, using data from the 2010-2011 to 2018-2019 California Healthy Kids Surveys (CHKS) of 9th and 11th grade students in 38 California cities. Multilevel mixed-effects logistic regression analyses were conducted, controlling for secular trends and student and city demographics. Additional analyses examined associations of RML and retail availability with co-use among subgroups of drinkers and marijuana users. For the full sample, RML was inversely associated with alcohol use but was not significantly associated with marijuana use or co-use with alcohol. However, significant interactions between RML and marijuana outlet density showed that there were increases in marijuana and alcohol co-use and alcohol following legalization in cities with higher densities of marijuana outlets. RML was positively associated with co-use among non-heavy and heavy drinkers, but inversely related to co-use among occasional and frequent marijuana users. A significant positive interaction between RML and marijuana outlet density indicated that RML was associated with increases in co-use for occasional marijuana users in cities with higher densities of marijuana outlets. RML was associated with increases in marijuana and alcohol co-use and alcohol use among California high school students, particularly those in cities with higher densities of retail cannabis stores, although this varied across alcohol and marijuana use subgroups.