Abstract
BACKGROUND: The relationships between cannabis use frequency with alcohol use, alcohol-related harms, and persistent alcohol use disorder (AUD) in a general population subsample of individuals previously treated for AUD were examined. METHODS: Secondary analyses of the 2005, 2010, and 2015 U.S. National Alcohol Surveys, a nationwide general population sample of individuals ages 18+, were performed. The analytic subsample (N = 772) reported 3+ lifetime DSM-IV alcohol dependence criteria and prior AUD treatment. Primary exposure was past 12-month frequency of cannabis use (weekly or more, or "heavy;" more than monthly/less than weekly or "midlevel;" less than monthly or "light;" none). Primary outcomes were past 12-month total volume, average frequency of 5+ drinks/month, past 12-month alcohol-related harms, and past 12-month DSM-IV alcohol dependence. RESULTS: Multivariable negative binomial and logistic regressions showed that the only cannabis users who consistently differed significantly from cannabis abstainers were midlevel users; specifically, more than monthly/less than weekly cannabis users drank 2.83 times as many drinks (95% CI: 1.43, 5.60); had 2.83 as many 5+ occasions (95% CI: 1.38, 5.79); had 6.82 times the odds of experiencing any harms (95% CI: 2.29, 20.33); and had 6.53 times the odds of persistent AUD as cannabis abstainers (95% CI: 2.66, 16.02; all ps < 0.05). The relationship between midlevel cannabis use and harms remained significant after adjustment for volume and frequency of 5+ (OR = 6.18, 95% CI: 1.35, 28.37). CONCLUSIONS: Among those with lifetime AUD who have been to treatment, only more than monthly/less than weekly cannabis use is related to more alcohol-related harms and persistent AUD compared to cannabis abstinence. Heavier and lighter cannabis use is not related to worse alcohol outcomes compared to cannabis abstinence.