Use of Tobacco and Cannabis Following State-Level Cannabis Legalization.

Importance: Cannabis use has been shown to modestly increase shortly after legalization of recreational use, but little is known about longer-term changes in cannabis and tobacco use. Objective: To assess the association of cannabis legalization and commercialization with the use of cannabis, cigarettes, and electronic nicotine delivery systems (ENDS) in the 5 years after legalization in the US. Design, Setting, and Participants: The Population Assessment of Tobacco and Health (PATH) study, a nationally representative longitudinal cohort study of adults 18 years or older in the US, was used for a retrospective, difference-in-differences analysis of panel data from January 2013 to December 2022. Data were analyzed from May 8, 2024, to April 20, 2025. Exposures: State-level recreational cannabis legalization (RCL) and opening of retail outlets with 5 years of follow-up. Main Outcomes and Measures: Percentage point changes in 30-day use of cannabis, cigarettes, and ENDS in states with legalization compared with control states, aggregated over 5 years and then broken down into the periods before and after retail outlets opened. Results: Among the 171 257 observations from 55 406 individuals included in the analysis (50.9% female; mean [SD] age, 37.97 [17.69] years), RCL was associated with an increase of cannabis use by 3.28 (95% CI, 2.29-4.27) percentage points and ENDS use by 1.39 (95% CI, 0.44-2.35) percentage points compared with control states. There was no differential change in cigarette use (-0.99 [95% CI, -2.25 to 0.27] percentage points). For cannabis, this change was greater after retail outlets opened (3.74 [95% CI, 2.65-4.82] percentage points) compared with before (1.17 [95% CI, 0.13-2.20] percentage points). There were no large changes in ENDS or cigarette use associated with the opening of retail outlets. Conclusions and Relevance: In this longitudinal cohort study, RCL was associated with more cannabis and ENDS use after 5 years and no significant change in cigarette use. Furthermore, cannabis use increased over time, underscoring the importance of studying commercialization policy going forward. Based on the present results, it is unlikely RCL has been associated with a large increase in cigarette use, but increases in use of cannabis and vaped nicotine bear close monitoring as retail cannabis rapidly expands.