Hierarchical and mediated relations between internalizing symptoms, alcohol and cannabis co-use, and AUD

Background Alcohol and cannabis co-use is associated with negative alcohol consequences and alcohol use disorder. However, mediating and distal effects remain largely unstudied. Co-use is associated with alcohol use disorder/negative consequences even when accounting for drinking levels and personality, suggesting that other person-level characteristics may explain relations between co-use and negative outcomes. Method The current study tested whether internalizing symptoms, strong correlates of co-use and alcohol use disorder, explained the effect of co-use on alcohol use disorder. Data from adults (N = 353,000) in the 2008-2019 National Study on Drug Use and Health (NSDUH) were used. Analyses tested whether (1) substance use profiles reduced/dissipated the effect of co-use on alcohol use disorder, (2) internalizing symptoms (anxiety, depression) reduced/dissipated the effect of co-use on alcohol use disorder, and (3) internalizing symptoms were indirectly associated with alcohol use disorder via co-use. Results When accounting for frequency/quantity of use, co-use was still associated with higher odds of alcohol use disorder. Anxiety and depression were related to higher odds of an alcohol use disorder, however, the effect of co-use on higher odds of alcohol use disorder remained. Anxiety and depression scores were indirectly associated with higher odds of alcohol use disorder via co-use. Conclusions Depressive and anxiety symptoms only accounted for a portion of the variance of co-use on alcohol use disorder, and there were indirect effects of internalizing symptoms through co-use. Future longitudinal research is needed to elucidate other person-level characteristics that drive associations between co-use and alcohol use disorder to target via interventions.