The Effect of Medical Cannabis Dispensaries on Opioid and Heroin Overdose Mortality

With over 42,000 deaths due to opioid overdoses in 2016, the ongoing opioid epidemic is arguably the most pressing public health crisis in the U.S. No policy has been successful in reducing opioid-related mortality overall, which is driven by an exponential increase in heroin and fentanyl (a synthetic opioid) overdoses in recent years. While not intended as a remedy for the opioid crisis, several studies have shown that the legalization of medical cannabis may alleviate this epidemic. These existing studies focus on the role of state laws that legalize the consumption of cannabis for medical purposes.

Departing from existing studies, our research design compares counties with and without dispensaries within the same state. Using a novel dataset that documents the locations and opening and closing dates of medical cannabis dispensaries, we capture changes in the effective costs of drug consumption that follow the implementation of medical cannabis laws (MCL). Therefore, we are not only able to control for the legal status of medical cannabis but also for any unobserved factors that may drive differences in opioid use between states. In addition, we allow for persistent unobserved county-specific differences and state-specific trends in opioid mortality. Hence, our identification strategy relies on temporal variation in the access to medical cannabis within counties. This research design allows us to isolate the impact of a dispensary on opioid-related deaths more effectively than prior literature and brings our estimates closer to providing a causal interpretation.

Using time variation in dispensary opening and estimating Poisson regressions of county-level deaths due to opioid overdoses, we find a significant decline in mortality in counties where dispensaries are present. While medical cannabis dispensaries reduce opioid-related mortality overall, our results are strongest for heroin overdoses. Specifically, we find that mortality related to any opioids and prescription opioids declines by 6% to 8%. For heroin, the r­­eduction in mortality amounts to 10%, although this effect is less precisely estimated. Importantly, these effects are limited to counties where dispensaries opened and do not apply to non-dispensary counties in states with that have legalized medical cannabis. In fact, with the exception of heroin-related overdoses, MCL themselves have a positive effect on opioid- related mortality. That is, while legalizing medical cannabis is not associated with lower levels of opioid overdose mortality, the presence of dispensaries has a large negative impact on the number of opioid-related deaths. These estimates imply that 10 per 100,000 (8.5%) fewer opioid-related deaths would have occurred between 1999 and 2015 if states that legalized medical cannabis during this period had had dispensaries in all counties as soon as the MCL came into effect.