Cannabis and alcohol co-use: The effects of intensity of cannabis use among heavy drinkers

Objective: Cannabis and alcohol co-use is highly prevalent and confers a host of risk factors that outweigh those related to the use of either substance alone. However, few studies have examined associations between varying levels of co-use intensity (i.e., frequency) and clinical variables. The present study characterizes the effects of co-use across varying levels of cannabis use frequency in a large sample of heavy drinkers. Methods: Comparisons among co-use groups (i.e., no, light-to-moderate, and moderate-to-heavy cannabis use; N = 863; 33.95 % female) on demographic and clinical variables consisted of one-way analyses of variance for continuous outcomes or Chi-Square tests for dichotomous outcomes. Multinomial logistic regression modeling was used to examine the relationship between demographic and clinical variables and co-use group membership. Multiple linear regression was used to explore associations among variables of interest and cannabis use days. Results: Despite relatively low levels of cannabis use overall in the present sample, younger age, identification with male gender, treatment seeking for AUD, and concurrent tobacco use were robust predictors of co-use. Individuals reporting more frequent cannabis use also reported increased levels of alcohol craving and more heavy drinking days, as compared to those who reported fewer or no cannabis use days. Drinking days and treatment seeking for AUD significantly predicted increases in cannabis use days. Conclusion: In clinical practice, younger age, male gender, and comorbid tobacco use represent identifiable risk factors for cannabis and alcohol co-use. While in treatment for AUD, reducing drinking days may be an inter-vention target to mitigate co-use.