Time Trends Matter: The Case of Medical Cannabis Laws and Opioid Overdose Mortality
Posted: 26 Jun 2018 Last revised: 7 Dec 2018
Date Written: June 22, 2018
Mortality due to opioid overdoses has been growing rapidly in the U.S., with some states experiencing much steeper increases than others. Legalizing medical cannabis could reduce opioid-related mortality if potential opioid users substitute towards cannabis as a safer alternative. I show, however, that a substantial reduction in opioid-related mortality associated with the implementation of medical cannabis laws can be explained by selection bias. States that legalized medical cannabis exhibit lower pre-existing mortality trends. Accordingly, the mitigating effect of medical cannabis laws on opioid-related mortality vanishes when I include state-specific time trends in state-year-level difference-in-differences regressions.
Keywords: medical cannabis laws, opioid overdose mortality, difference-in-differences, group-specific time trends
JEL Classification: C23, I12, I18, K32
Suggested Citation: Suggested Citation