In a lab study, cannabis did not increase later cigarette or vape use

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).