Adult use cannabis legalization and cannabis use disorder treatment in California, 2010-2021

Introduction: Many nations and jurisdictions have legalized non-medical adult use of cannabis, or are considering doing so. This paper contributes to knowledge of adult use legalization's associations with cannabis use disorder (CUD) treatment utilization. Methods: This study collected data from a dataset of all publicly funded substance use disorder treatment delivered in California from 2010 to 2021 (1,460,066 episodes). A logistic regression model estimates adult use legalization's impacts on CUD treatment utilization using an individual-level pre-post time series model, including individual and county-level characteristics and county and year-fixed effects. Results: Adult use legalization was associated with a significant decrease in the probability of admission to CUD treatment (average marginal effect (AME): -0.005, 95 % CI: -0.009, 0.000). Adult use legalization was also associated with a decrease in the probability of admission to CUD treatment for males (AME: -0.025, 95 % CI: -0.027, -0.023) Medi-Cal beneficiaries (AME: -0.025, 95 % CI: -0.027, -0.023) adults ages 21+ (AME: -0.011, 95 % CI: -0.014, -0.009) and Whites (AME: -0.012, 95 % CI: -0.015, -0.010), and an increase in the probability of admission to CUD treatment for patients referred from the criminal justice system (AME: 0.017, 95 % CI: 0.015, 0.020) and Blacks (AME: 0.004, 95 % CI: 0.000, 0.007) and Hispanics (AME: 0.009, 95 % CI: 0.006, 0.011). Conclusions: Adult use legalization is associated with declining CUD treatment admissions, even though cannabisrelated problems are becoming more prevalent. Policies and practices that protect public health, and engage people with CUD in treatment are needed.