Recreational cannabis legalisation has been associated with increases in adult cannabis use. However, it is unclear whether legalisation is driving the rising levels of co-use of tobacco and cannabis.
We linked 2016–2023 Behavioural Risk Factor Surveillance System data on 854 878 adults aged 18+ years from 38 states with data on state recreational cannabis legalisation and retail sales availability. Using multinomial logit regression models, we examined the associations between legalisation and the use and co-use of tobacco and cannabis overall and by demographic (age, sex, education, race and ethnicity) and higher-risk (mental health, alcohol use) strata, with demographic and policy controls and state and year fixed effects.
Recreational cannabis legalisation was associated with overall increases in cannabis-only use (adjusted relative risk ratio (aRRR) 1.88; 95% CI 1.78 to 1.99) and co-use of tobacco and cannabis (1.44; 1.34 to 1.54) compared with no use, and with decreases in tobacco-only use (0.87; 0.83 to 0.91). Similar patterns emerged in response to the start of cannabis retail sales. There was some evidence of increases in co-use of tobacco and cannabis post-legalisation and/or retail sales among adults aged 18–24 and 55+ years, with a high school degree or higher, and who identified as White or Black. No differential effects for co-use emerged across higher-risk strata.
Recreational cannabis legalisation is increasing cannabis-only use and co-use of tobacco and cannabis, including rises in co-use among populations with lower levels of cannabis use. Increased surveillance of and screening for co-use of tobacco and cannabis can help inform public health responses to legalisation.