Do Medical Marijuana Laws Reduce Addictions and Deaths Related to Pain Killers?

This study looks at the impact of laws legalizing medical marijuana dispensaries on addictions and deaths related to pain relievers, such as opioids.  Opiate abuse, disorders, and overdoses have become a significant medical and public health problem.  The number of fatal poisonings due to prescription pain medications has quadrupled between 1999 and 2010.  Using the Treatment Episode Data Set (TEDS), we find that treatment for substance abuse of prescription pain relievers increased by 700% between 1992 and 2010 while total substance abuse treatments grew by only 20%.  It is rare to find differential availability of alternative treatments for pain management, but we exploit state-level legalizations of medical marijuana dispensaries as exogenous increases in availability of an alternative treatment.  Reports from medical marijuana patients suggest that marijuana is often used to alleviate pain from musculoskeletal problems and other chronic pain.  Hence, marijuana might serve as a substitute for many powerful and addictive pain relievers, when available for medicinal purposes.  We use the Treatment Episode Data Set (TEDS) to calculate the frequency of treatments due to pain reliever addiction.  To complement this analysis, we use state-level mortality data from the National Vital Statistics System (NVSS).   The mortality data provide information on the reason for death, which we use to determine deaths related to the use of opioids.  We first estimate standard differences-in-differences models to exploit changes in state dispensary policy to test for differential changes in our outcomes.  Given concerns that the adopting states may not be similar to all non-adopting states, we also implement a synthetic control approach.  The results are similar using both methods. We find evidence that states permitting dispensaries experience a relative decrease in both addictions and deaths.   These reductions are large and statistically significant.