Subgroup trends in alcohol and cannabis co-use and related harms during the rollout of recreational cannabis legalization in Washington state

Subbaraman, Meenakshi S.; Kerr, William C.

Background: The US state of Washington legalized recreational cannabis in 2012; how this impacted the co-use of cannabis and alcohol in the population overall and among key subgroups has not been examined. The aim of this study is to investigate changes in patterns of alcohol- and cannabis use and alcohol-related harms during the rollout of retail recreational cannabis stores. Methods: Data come from six cross-sectional samples recruited between January 2014-October 2016 via Random Digit Dial procedures (N = 5492). Survey-weighted multivariable regression adjusting for gender, age, race/ethnicity, education, employment, marital status, cannabis use, and survey year were used for statistical analyses. Results: In the sample overall, no significant changes were observed in any alcohol use measures between 2014-2016, while the prevalence of cannabis use significantly (P < 0.05) increased from 25.0% to 31.7%, the prevalence of alcohol-related harms at home significantly decreased from 2.1% to 1.0%, and the prevalence of alcohol-related financial harms decreased from 1.5% to 0.8%. Both women and men significantly increased any cannabis use, while women also experienced significantly fewer alcohol-related harms at home and financial harms over time, and increases in the prevalence of cannabis users/non-drinkers. Those 18-29 years old significantly reduced the number of drinking days and overall volume in the past 30 days, and those 30-49 years old significantly decreased alcohol-related harms at home and financial harms. Those 50 + years old significantly increased any cannabis use and simultaneous use of cannabis and alcohol. Non-cannabis users slightly decreased average number of drinks/day, and cannabis users significantly decreased alcohol-related financial harms. Conclusions: Between 2014-2016, the years during and immediately following the introduction of legal recreational cannabis stores in Washington state, there were no significant changes in cannabis and alcohol co-use or overall alcohol consumption. The only significant changes in the sample overall were an increase in any cannabis use and decreases in alcohol-related harms at home and alcohol-related financial harms.