Patterns of Cannabis and Alcohol Co-Use: Substitution Versus Complementary Effects

Abstract

PURPOSE The purpose of this review is to discuss the literature regarding the concurrent use (co-use) of alcohol and cannabis and competing hypotheses as to whether cannabis acts as a substitute for (i.e., replacing the effects of alcohol, resulting in decreased use) or a complement to (i.e., used to enhance the effects of alcohol, resulting in increased use) alcohol. The impact of cannabis use on alcohol-related outcomes has received increased attention in the wake of ongoing legalization of cannabis for both medical and recreational purposes. Evidence for both hypotheses exists in the literature across a broad range of data collection methods and samples and is carefully reviewed here. In addition, various mechanisms by which cannabis may act as an alcohol substitute or complement are explored in depth with the goal of better understanding equivocal findings. SEARCH METHODS This review includes articles that were identified from a search for studies on alcohol and cannabis co-use, with a specific focus on studies exploring complementary versus substitution aspects of co-use. Search terms were included in Google Scholar, PsycINFO, MEDLINE, and Web of Science. Eligible studies were those that measured alcohol and cannabis co-use in human samples in laboratory, survey, or ecological momentary assessment studies, or that directly referenced substitution or complementary patterns of use. SEARCH RESULTS Search results returned 650 articles, with 95 meeting inclusion criteria. DISCUSSION AND CONCLUSIONS Results of this review reveal compelling evidence for both substitution and complementary effects, suggesting nuanced yet significant distinctions across different populations examined in these studies. Several mechanisms for the impact of cannabis use on alcohol-related outcomes are identified, including patterns and context of co-use, timing and order of use, cannabinoid formulation, pharmacokinetic interactions, and user characteristics (including diagnostic status), all of which may influence substitution versus complementary effects. This review will inform future research studies examining this topic in both clinical and community samples and aid in the development of treatment and prevention efforts targeting those populations most vulnerable to negative consequences of co-use. Finally, this review highlights the need for additional research in more diverse samples and the use of mixed-methods designs to examine both pharmacological and contextual influences on co-use.

Cross-substance primed and cue-induced craving among alcohol and cannabis co-users: An experimental psychopharmacology approach.

“…While pharmacologically induced cross-substance craving was not observed, participants showed a robust cue-reactivity response to the alcohol/cannabis cues presented, at the detriment of cross-substance craving. These findings add to the literature on extant mechanisms of co-use (Gunn et al, 2022; Risso et al, 2020; Subbaraman, 2016). Specifically, they show limited support for a complementarity hypothesis and instead may provide more evidence for substitution, such that the newly available substance was on average preferable, regardless of prior substance administration.…”

“…Two prominent proposed models of co-use include those related to the complementary or additive effects of alcohol and cannabis (i.e., complementarity, resulting in increased use) and those related to the use of one substance as a pharmacological substitute for the other (i.e., substitution, resulting in decreased use; Subbaraman, 2016). Whether alcohol and cannabis are considered complements to or substitutes for one another remains a widely debated topic, with mixed evidence for both models (Gunn et al, 2022; Risso et al, 2020; Subbaraman, 2016). In fact, systematic reviews by Subbaraman (2016) and Risso et al (2020) have posited that while the literature tends to generally provide stronger support for substitution over complementarity, effects vary by population (i.e., age and race/ethnicity).…”

“…In fact, systematic reviews by Subbaraman (2016) and Risso et al (2020) have posited that while the literature tends to generally provide stronger support for substitution over complementarity, effects vary by population (i.e., age and race/ethnicity). An additional review by Gunn et al (2022) also revealed evidence for both models of co-use, suggested that there are nuanced effects across populations, and identified various potential moderators of whether cannabis acts as a substitute for or complement to alcohol (e.g., differing cannabis formulations, variations in age, and motivations for use). As such, more research aimed at providing a clearer understanding of these mechanisms is warranted.…”

Alcohol and Cannabinoids - From the Editors

“… 30 Lees, Debenham, and Squeglia present a comprehensive overview of longitudinal neuropsychological and neuroimaging studies on the independent and combined effects of cannabis and alcohol use on the developing human brain. 31 Several articles review findings on the impact of cannabis use on alcohol consumption and consequences, and how this association may differ by cannabis formulation or by user characteristics, 32 with a specific focus on simultaneous alcohol and cannabis use, and contextual characteristics of co-use in young adults. 33 Finally, Pacula et al provide a systematic review of published studies on the effect of liberalization of cannabis policies on alcohol use and co-use with cannabis in the United States and Canada.…”