The effects of simultaneous alcohol and cannabis use on subjective drug effects: A narrative review across methodologies

Abstract

Over 75% of young adults who use cannabis also report drinking alcohol, leading to increased risks including impaired cognition, substance use disorders, and more heavy and frequent substance use. Studies suggest subjective responses to either alcohol or cannabis can serve as a valuable indicator for identifying those at risk of prolonged substance use and use disorder. While laboratory studies suggest additive effects when using alcohol and cannabis together, the impact of co-using these substances, specifically with respect to cannabidiol, on an individual's subjective experience remains unclear. This narrative review explores the effects of simultaneous alcohol and cannabis (SAM) use on subjective drug effects, drawing from qualitative research, laboratory experiments, and naturalistic studies. Experimental findings show inconsistency in the combined effects of alcohol and cannabis, likely influenced by factors such as dosage, method of administration, and individual substance use histories. Similarly, qualitative and naturalistic studies show mixed results regarding subjective drug effects following simultaneous alcohol and cannabis use. These discrepancies may be due to recall biases, variations in assessment methods and how patterns of SAM use and related experiences are measured in real-world contexts. Overall, this narrative review highlights the need for more comprehensive research to better understand subjective drug effects related to the SAM use in diverse populations and settings, emphasizing the importance of frequent and nuanced assessment of SAM use and subjective responses in naturalistic settings.