Dustin C. Lee

Co-use of smoked/vaped tobacco and cannabis is increasing with expanding legalization, yet controlled clinical studies examining mechanisms underlying co-use remain limited. This study evaluated whether acute smoked cannabis influences subsequent use ("chasing") of combustible cigarettes and e-cigarettes among people who use cannabis, cigarettes, and e-cigarettes. Twenty adults who used cannabis, cigarettes, and e-cigarettes completed seven double-blind outpatient sessions; six used cannabis infrequently (i.e., ≤2 times per week), and 14 used cannabis frequently (i.e., >2 times per week). Participants smoked THC-dominant cannabis (10 mg for infrequent; 25 mg for frequent use) or placebo (0 mg THC) and then had 5-hr ad libitum access to their preferred cigarette brand or a JUUL e-cigarette (3% or 5% nicotine). A THC-dominant cannabis-only condition served as a control. Primary outcomes included cannabis and nicotine use behavior (puff topography, time-to-first use) and acute subjective, cognitive, and physiological effects. Cannabis administration increased subjective drug effects (e.g., drug liking, pleasant effects) and heart rate compared with placebo, as expected. However, the time course and magnitude of subjective and physiological effects following ad libitum e-cigarette or cigarette use did not differ between the cannabis and placebo conditions. Likewise, cannabis did not alter ad libitum cigarette or e-cigarette puff topography relative to placebo. Cannabis exposure did not increase nicotine use behavior, and neither cigarette nor e-cigarette use enhanced or extended acute cannabis effects in this laboratory model of chasing. Modeling naturalistic cannabis-tobacco co-use in controlled settings remains challenging. Further research examining simultaneous use and alternative sequencing patterns is needed to clarify mechanisms underlying co-use behaviors. (PsycInfo Database Record (c) 2026 APA, all rights reserved).

Background: Tobacco and cannabis are among the most widely used substances globally, and rates of co-use are on the rise. Understanding the impact of inhaled tobacco-cannabis co-use on health outcomes and tobacco cessation is critical for guiding patients and clinicians. Objectives: To summarize the existing evidence, identify knowledge gaps, and prioritize research questions related to effects of inhaled tobacco-cannabis co-use on tobacco cessation and lung health. Methods: A multidisciplinary committee was convened to review the evidence, identify knowledge gaps, and develop research questions in four priority research areas: 1) common data elements and terminology, 2) patterns and prevalence of co-use, 3) impact of co-use on tobacco cessation, and 4) effects of co-use on lung health. A modified Delphi process was conducted in three rounds to reach consensus on prioritizing research questions. Results: The evidence reviewed by the expert panel in four priority research areas yielded the following gaps in the literature with high priority to address with future research: 1) lack of consensus on terminology and recommended co-use data elements, 2) limited research on co-use and tobacco-related disparities, 3) insufficient evidence on how cannabis use affects tobacco cessation, and 4) alarming yet inconsistent findings on the effects of co-use on lung health. Conclusions: This statement outlines and guides a research agenda on the effects of inhaled tobacco-cannabis co-use on tobacco cessation and lung health. Consensus-driven recommendations include adopting harmonized terms and minimum data elements, studying the prevalence of co-use among populations experiencing tobacco-related disparities, evaluating the impact of co-use on tobacco cessation pharmacotherapies, and assessing the effects of co-use on the development and progression of lung diseases.

The cannabis gray market poses significant public health concerns and remains a major threat to consumer and/or potential consumer uptake of regulated cannabis markets in jurisdictions with legal state-sponsored cannabis programs. In this perspective, we provide an overview of the cannabis gray market, and describe an integrated epidemiological and regulatory science framework to study the gray market. Using tobacco regulatory science as a guide, we introduce example cannabis regulatory science research activities as a means to improve the field’s understanding of the cannabis gray market. Cannabis regulatory science is a developing field that can improve our understanding of the cannabis regulatory ecosystem and provide regulatory officials and policymakers alike with much needed data to inform regulatory decision-making and improve the success and uptake of state-sponsored cannabis programs.

Purpose of Review The goal of this article is to summarize the treatment-focused literature on cannabis and tobacco co-use and the treatment implications of co-use. This review will focus on the following: (1) the impact of co-use on cessation outcomes, (2) compensatory use/substitution of the non-treated substance among co-users, and (3) treatment interventions to address co-use. This article will highlight the limitations to co-use captured in the literature and offer considerations and directives for co-use research and treatment moving forward. Recent Findings The degree to which co-use affects cessation for a single, targeted substance remains in question, as the literature is largely mixed. Cannabis treatment trials are better equipped to answer these questions given that they do not typically exclude tobacco users. While the relationship between tobacco use and poorer cannabis outcomes appears to have some evidence, the reverse relationship (cannabis use affecting tobacco outcomes) is not consistently supported. Summary The co-use of cannabis and tobacco and its impact on single substance cessation and/or compensatory substance use during cessation is generally overlooked in treatment trials, while interventions to address both substances are rare. Capturing co-use adds burden for researchers, clinicians, and participants, but is warranted given the prevalence of co-use and a rapidly changing cannabis and tobacco regulatory environment, which may further complicate co-occurring substance use. Co-users are a heterogeneous population; trials focused on co-users, in addition to better data capture and consistent terminology, will aid in an understanding of nuanced patterns of co-use critical to inform treatment interventions.