Effects of Legal-Market Cannabis and Alcohol on Verbal Learning and Memory

Rationale. Concurrent with widespread legalization of cannabis in recent years, US adults are increasingly using alcohol and cannabis at the same time. Cannabis is thought to confer synergistic effects on alcohol intoxication, and the potential for increased cognitive impairment is a primary concern. Most co-administration studies to date have relied on low-THC cannabis, limiting generalizability to real-world consumption of higher-THC, legal-market cannabis products.Objectives. We aimed to test whether legal-market flower cannabis confers verbal learning and memory impairment over and above the effects of an acute dose of alcohol in a sample of heavy-drinking community participants who also report regular cannabis use. Methods. Participants (n=60, 40% female) completed two sessions in our mobile laboratory: an Alcohol-Only session and a Cannabis+Alcohol session. At each session, participants completed the Rey Auditory Verbal Learning Test (RAVLT) before and after substance use. Linear mixed-effects models evaluated effects of substance use condition and sex on RAVLT performance, controlling for demographic covariates.Results. We observed a 6% decrease in RAVLT performance in the Cannabis+Alcohol session compared to the Alcohol-Only session (p<.001). This effect was stronger in females than males (p=.003) for RAVLT trials prior to interference, but no sex differences emerged for post-interference trials. Conclusions. Consistent with our hypotheses, we found that legal-market cannabis is associated with acute verbal learning and memory impairments compared to alcohol alone, with females showing heightened vulnerability dur-ing the initial memory encoding phase. Results highlight the risks of alcohol and cannabis co-use and underscore the importance of studying high-THC cannabis products.