Recreational marijuana laws reduce annual opioid mortality in the range of 20%–35%, with particularly pronounced effects for synthetic opioids

The Effects of Recreational Marijuana Legalization and Dispensing on Opioid Mortality. Nathan W. Chan, Jesse Burkhardt, Matthew Flyr. Economic Enquiry, August 6 2019. https://doi.org/10.1111/ecin.12819

Abstract: This study documents how the changing legal status of marijuana has impacted mortality in the United States over the past two decades. We use a difference‐in‐difference approach to estimate the effect of medical marijuana laws (MML) and recreational marijuana laws (RML) on fatalities from opioid overdoses, and we find that marijuana access induces sharp reductions in opioid mortality rates. Our research corroborates prior findings on MMLs and offers the first causal estimates of RML impacts on opioid mortality to date, the latter of which is particularly important given that RMLs are far more expansive in scope and reach than MMLs. In our preferred econometric specification, we estimate that RMLs reduce annual opioid mortality in the range of 20%–35%, with particularly pronounced effects for synthetic opioids. In further analysis, we demonstrate how RML impacts vary among demographic groups, shedding light on the distributional consequences of these laws. Our findings are especially important and timely given the scale of the opioid crisis in the United States and simultaneously evolving attitudes and regulations on marijuana use. (JEL I18, K32, H75)

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Why "the scale of the opioid crisis in the" US? Why are you working in this area and know not of other places with similar issues? Less passion and more data, it is happening also in parts of the UK (https://www.nytimes.com/2019/08/07/world/europe/scotland-heroin-deaths.html).