Legal Recreational Cannabis Sales and Opioid-Related Mortality in the 5 Years Following Cannabis Legalization in Canada: A Granger Causality Analysis.

Objective: Little is known about the population-level impact of recreational cannabis legalization on trends in opioid-related mortality. Increased access to cannabis due to legalization has been hypothesized to reduce opioid-related deaths because of the potential opioid-sparing effects of cannabis. The objective of this study was to examine the relations between national retail sales of recreational (non-medical) cannabis and opioid overdose deaths in the 5 years following legalization in Canada. Method: Using time-series data, we applied Granger causality methods to evaluate the association between trends in legal recreational cannabis sales and opioid-related deaths over time. Both sales and opioid deaths grew over time, with the latter exhibiting significant increases following the onset of the COVID-19 pandemic. Results: We found no support for the hypothesis that increasing post-legalization sales Granger caused changes in opioid-related deaths in British Columbia, Ontario, or at the national level. Conclusions: These findings suggest that increases in legal recreational cannabis sales following legalization were not meaningfully associated with changes in opioid-related mortality. Further examination with longer follow-up periods will be needed as the legal cannabis market becomes more entrenched in Canada, but these findings converge with previous work suggesting legalization is not related to opioid overdose mortality and further undermine that hypothesized link as a basis for legalization in other jurisdictions.