Prior research on the association between state cannabis policies and opioid-related mortality has been mixed and limited by within-state policy variation and an inconsistent association between policies and actual cannabis availability. This study used panel regression methods to report on the association between opioid-related mortality and county-level cannabis dispensary counts, a fairly direct measure of cannabis availability at the local level. Dispensary counts and locations in 23 US states (814 counties) that allow medical or non-medical cannabis were obtained from Weedmaps, a major US cannabis website, for the period 2014–2018.
- After controlling for county-level population characteristics, yearly effects, and local and state cannabis and prescription opioid policies, an increase from one to two cannabis dispensaries at the county level was associated with a 17% reduction in overall age-adjusted opioid mortality rates.
- The association between dispensary counts and deaths associated with synthetic (non-methadone) opioids (including fentanyl) was greater (21% reduction with an increase from one to two dispensaries) than for deaths from prescription opioids or heroin (both an 8% reduction).
- Findings were similar when separating medical versus non-medical cannabis dispensaries, and when all US counties were included in the analysis.
Comments: This study provides the most detailed data to date in support of the association between legal cannabis availability and opioid-related mortality, with a particularly strong association with synthetic opioids, which includes fentanyl. The validity of the cannabis dispensary data used in this study is uncertain, and unmeasured confounding—perhaps related to opioid use disorder treatment access—remains a possible explanation for these findings. Moreover, this study highlights the complexity of overlapping drug markets and their associations with adverse health outcomes.
Joseph Merrill, MD, MPH
Reference: Hsu G, Kovács B. Association between county level cannabis dispensary counts and opioid related mortality rates in the United States: panel data study. BMJ. 2021;372:m4957.