Alcohol use and risk of related problems among cannabis users is lower among those with medical cannabis recommendations, though not due to health (2018)

Objective: A small body of work has started developing cannabis use "typologies" for use in treatment and prevention. Two potentially relevant dimensions for classifying cannabis use typologies are medical versus recreational cannabis use and the co-use of cannabis and alcohol. Here we compare alcohol use and related problems between cannabis users with and without medical cannabis recommendations.
Method: Data come from a larger general population study in Washington State conducted between January 2014 and October 2016. All participants in the analytic sample (n = 991) reported using both alcohol and cannabis in the past 12 months. The primary exposure was having a medical recommendation for cannabis. Outcomes were past-30-day drinking (drinks/day, frequency of 5+ drinks, and maximum number of drinks in a day) and past-12-month Alcohol Use Disorders Identification Test (AUDIT) scores.
Results: Compared with those without medical cannabis recommendations, cannabis users with medical cannabis recommendations had 0.59 times fewer drinks/day, 0.44 times fewer occasions drinking 5+, and 0.78 times the average maximum number of drinks in one day (all ps < .05). Those with a recommendation also had 0.87 times lower AUDIT total scores (p < .05) and 0.57 times lower AUDIT problem scores (p < .01).
Conclusions: Cannabis users with medical cannabis recommendations drink less and have fewer alcohol-related problems than those without recommendations, even after adjusting for health status. Future studies should examine nonhealth reasons regarding how medical and nonmedical users use cannabis differently.