The Impact of Medical Marijuana Access on the Health and Labor Supply of Older Adults

Decriminalization of marijuana for medicinal or recreational use is one of the most controversial issues in state and Federal drug policy.  Marijuana has been shown to alleviate chronic pain and nausea and stimulate appetite among patients with difficulty eating, offering a promising therapeutic option for many chronic illness patients.  However, any therapeutic gains must be weighed against the potential for adverse effects of broadened marijuana access including adverse physical and cognitive effects, public safety problems if users are driving or operating machinery under the influence, and greater recreational marijuana use. 

23 states and the District of Columbia have legalized medical marijuana since 1996.  However, the effects of these laws are largely unknown.  The economics literature has largely focused on unintended consequences of medical marijuana laws, with a particular focus on teenagers and young adults.  However, the therapeutic benefits of medical marijuana are likely concentrated among older adults, who have high rates of arthritis, back pain, and other conditions that respond to medical marijuana.  With nearly half of registered medical marijuana users age 50 and over, we study the effect of state medical marijuana laws (MML) on the prevalence of back pain, depressive symptoms, and labor supply among older adults.  

We use nationally representative Health and Retirement Study panel survey data from 1992 – 2012 to estimate difference-in-differences regressions of respondent-level outcomes on state law changes.  Our intent-to-treat estimates suggest that legalizing medical marijuana decreases the share of older adults reporting back pain symptoms by 1.2 – 2 percentage points (p < 0.05) and increases the proportion working for pay by 1.5 percentage points (p < 0.10).  Findings are robust across a number of coding schemes used by other papers in the literature and persist across specifications with state or respondent-level fixed effects, and allowing separate time trends for states that ever adopt MMLs.  Subgroup analyses will test the impact of MMLs on patient populations most likely to benefit from marijuana access including those with chronic pain and current cancer treatments. 

The improvements in pain and labor supply are accompanied by a modest increase in depressive symptoms including a 1.2 percentage point decrease in the probability of feeling happy in the past two weeks (p < 0.01) and a 0.7 percentage point increase in feeling depressed (p < 0.10 Our results indicate that access to medical marijuana has benefits for older adults, though there may be unintended health consequences from changing the way pain is treated in this population.