Cannabis legalization and changes in cannabis and tobacco/nicotine use and co-use in a national cohort of U.S. adults during 2017-2021

Background: Little is known about whether cannabis legalization impacts cannabis use uptake or has spillover effects on co-use of cannabis and tobacco/nicotine (using both in the past 30 days). We determined associations of cannabis legalization with self-reported (1) current (past 30-day) cannabis use; (2) current ("now") tobacco/nicotine use (smoking or electronic cigarette use); and (3) current co-use of cannabis and tobacco/nicotine and how prevalence is changing over time.

Methods: In this longitudinal study, a web-based survey was administered to a nationally representative, population-based panel of US adults in 2017, 2020, and 2021. We used weighted unadjusted binomial logistic GEE models to assess changes in prevalence of cannabis, tobacco/nicotine use and co-use and weighted, adjusted binary logistic GEE models to assess associations of cannabis legalization with cannabis, tobacco/nicotine use and co-use.

Results: A total of 9003 participants (age range = 18-94, mean age = 47.9 [±17.4 SD] years; 4696 females [weighted 52.0 %]) completed the survey in 2017; 5979/8529 (70.1 %) in 2020 and 5420/7305 (74.2 %) in 2021 from the original cohort who remained available. Current cannabis use significantly increased +3.3 % between 2017 and 2021, while tobacco/nicotine use significantly declined (-1.9 %); co-use of cannabis and tobacco/nicotine did not change significantly (+0.2 %). Both medical and recreational cannabis legalization was associated with increased current cannabis use; the independent effect of recreational cannabis legalization was 1.13 times larger than medical. There were no statistically significant differences in tobacco/nicotine use and co-use prevalence by legalization status.

Conclusion: Cannabis legalization increases cannabis use but is not associated with changes in tobacco/nicotine use or co-use. Legalization should be coupled with public health efforts.