Emergency department use by individuals with and without psychosis after state-level cannabis legalization and commercialization.

Recreational cannabis legalization and commercialization are expanding rapidly in the USA, with potential negative effects for individuals with psychotic disorders. Here, to assess potential health risks associated with the opening of cannabis retail outlets, we conducted a longitudinal cohort study using a nationally representative survey to evaluate trends in emergency department utilization among individuals with psychosis compared with the general population with 3 years of follow-up. Data collection occurred in 2013-2022. Utilizing difference-in-difference (DiD) methods, we found that the opening of cannabis retail outlets was associated with an overall increase in emergency department visits among individuals with psychosis in legalization states (DiD estimate of 0.43 more visits per-person per-year, 95% CI -0.014 to 0.85, P = 0.043) but not among those with no history of psychosis (DiD estimate -0.015, 95% CI -0.03 to 0.06, P = 0.54). Exploratory analyses found this change was driven by more emergency department utilization among individuals with psychosis and past-year cannabis use, and not among other subgroups. This provides early evidence that cannabis commercialization is associated with worsening health among individuals with psychosis, and indicates a need for researchers, regulators and policymakers to collaborate to develop policies to minimize harms of cannabis legalization and commercialization among individuals with serious mental illnesses.