Marijuana's Impact on Alcohol Motivation and Consumption

This laboratory study will employ a repeated measures experimental design to examine the effect of high (7.2% THC) and moderate (3.1% THC) dose of marijuana, relative to placebo, on alcohol craving and on behavioral economic measure of alcohol demand after exposure to alcohol cues, and on subsequent drinking in an alcohol choice task in which participants choose either to drink or receive monetary reinforcement for drinks not consumed. Moderators of the marijuana's effects on alcohol-related dependent variables will be tested: DSM5 alcohol use disorder severity, affective vulnerability, trait impulsivity, and working memory functioning. Several empirically-determined mechanisms that may explain why marijuana may increase risk of alcohol relapse and help maintain heavy drinking will be tested as mediators of marijuana's effects on alcohol. The study will recruit 173 non-treatment seeking heavy episodic alcohol drinkers who smoke marijuana at least twice weekly to obtain the final sample of 150 with complete data (15% of attrition). Participants will be tested at a baseline session and during three experimental sessions. Investigators will collect blood samples for analysis of cannabinoid plasma levels and to examine marijuana-induced changes in hormones and other biomarkers potentially related to appetite, inflammation and stress. Collection of these biomarkers would allow for a greater understanding about the mechanisms whereby marijuana may acutely increase alcohol motivation and use. The findings will inform researchers and clinicians about how marijuana acutely increases alcohol craving and consumption. The strategy of this proposal is to use the most comprehensive controlled test characterizing marijuana's putative effects on alcohol.