(043) Association of Recreational and Medical Cannabis Legalization with Opioid Prescribing and Mortality: A Generalized Difference-In-Difference Analysis

Publication Number: 706

Background: While some have argued that cannabis legalization has helped to reduce opioid-related morbidity and mortality in the United States, evidence is mixed. Moreover, existing studies have not accounted for biases that could arise when the law’s effects vary over time or across states or when multiple laws are simultaneously assessed, as in the case of recreational and medical cannabis legalization.

Objectives: To quantify changes in opioid prescribing and opioid overdose deaths associated with recreational and medical cannabis legalization in the US.

Methods: Quasi-experimental, generalized difference-in-differences (DD) analysis using annual state-level data to compare states legalizing recreational or medical cannabis versus those that did not. The intervention was recreational and medical cannabis law implementation between 2006 and 2020 across US states. Outcomes included opioid prescribing rates per 100 persons and opioid overdose deaths per 100,000 population based on data from the U.S. Centers for Disease Control and Prevention.

Results: Between 2006 and 2020, 13 states legalized recreational and 23 states legalized medical cannabis. There was no statistically significant association of recreational or medical cannabis laws with opioid prescribing or overall opioid overdose mortality across the fifteen year study period, although the results also suggested a potential reduction in synthetic opioid deaths attributable to recreational cannabis laws (4.9 fewer deaths per 100,000 population; 95% CI, -9.49 to -0.30; P=0.04). Sensitivity analyses excluding state economic indicators, opioid laws and using alternative ways to code treatment dates yielded substantively similar results, suggesting the absence of statistically significant associations between cannabis laws and the outcomes of interest over the full study period.

Conclusions: After accounting for biases due to possible heterogeneous effects and simultaneous assessment of both recreational and medical cannabis legalization, the implementation of recreational or medical cannabis laws was not associated with opioid prescribing or opioid mortality, with the exception of a possible reduction in synthetic opioid deaths associated with recreational cannabis law implementation.