Cannabis administration is associated with reduced alcohol consumption and craving: Evidence from a novel laboratory co-administration paradigm

Background: Alcohol and cannabis co-use is increasingly prevalent across the U.S., concomitant with trends towards recreational cannabis legalization. While some studies have shown that cannabis co-use is associated with reductions in alcohol consumption (i.e., substitution), others have observed increases in alcohol intake (i.e., complementarity) or no change. This study aims to address this gap in the literature through investigating effects of legal-market cannabis and alcohol co-administration on alcohol consumption and craving. Method: Leveraging a within-subjects design, we enrolled non-treatment seeking individuals who co-use alcohol and cannabis (n=62) to complete two laboratory sessions, wherein they were provided an alcohol priming drink alone or after self-administering cannabis. Participants were then given the opportunity to self-administer up to 4 additional drinks. We assessed changes in alcohol self-administration and craving between sessions. Results: Cannabis self-administration was associated with a significant reduction in number of drinks self-administered and a significant acute reduction in craving. Further, individuals who drank less after using cannabis (n=23) experienced reductions in craving after using cannabis and alcohol compared to alcohol-alone, whereas individuals who drank the same number of drinks or more after using cannabis experienced minimal changes in craving. There were no significant group differences in blood-THC concentration post-cannabis use. Conclusion: Results indicate that for some individuals who drink heavily, cannabis may serve as a substitute for alcohol, and craving reduction may be the mechanism through which this occurs.