A study that examined older Americans' well-being before and after medical marijuana laws were passed in their state found reductions in reported pain and increased hours worked. The study, co-written by researchers at Johns Hopkins Bloomberg School of Public Health and Temple University, suggests medical marijuana laws could be improving older Americans' health.

The paper analyzed more than 100,000 responses from survey participants age 51 and older from 1992 to 2012. Researchers found a 4.8 percent decrease in reported pain and a 6.6 percent increase in reported very good or excellent health among respondents with a health condition that would qualify for medical marijuana after their states passed medical marijuana laws relative to similar respondents whose states did not pass a law.

The study appears in the Spring 2019 issue of the Journal of Policy Analysis and Management.

"Our study is important because of the limited availability of clinical trial data on the effects of medical marijuana," says Lauren Hersch Nicholas, PhD, assistant professor in the Bloomberg School's Department of Health Policy and Management. "While several studies point to improved pain control with medical marijuana, research has largely ignored older adults even though they experience the highest rates of medical issues that could be treated with medical marijuana."

Medical marijuana remains controversial as national support for it surges. Opponents continue to argue that legalizing medical marijuana would promote illegal use of the drug and increase misuse of related substances. Supporters highlight the potential health benefits of medical marijuana for pain management and other conditions. By the end of 2018, 33 states and Washington, D.C. had passed laws legalizing medical use of marijuana.

For their study, researchers used data from the 1992-2012 Health and Retirement Study (HRS), the largest nationally representative survey to have track health and labor market outcomes among older Americans. The researchers examined survey responses about symptoms that have a plausible link to one's ability to work: frequency of pain, whether health limits work, overall health assessment and depressive symptoms. At the time of the analysis, 20 states had medical marijuana laws in place.

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The analysis matched medical marijuana law effective dates to the HRS interview responses, based on month and year, to track the possible effects of these policy changes. The analysis used 100,921 participant responses that represented individuals with one or more of four health conditions that would qualify for medical marijuana treatment under most state laws (arthritis, cancer, glaucoma and pain). The paper found that 55 percent of the study sample were suffering from one or more of these diagnoses.

The study found that medical marijuana laws lead to increases in full-time work in both samples.

In the sample that would qualify for medical marijuana treatment, the researchers found a greater increase in full-time work after medical marijuana laws were passed. In the full sample, researchers found a 5 percent increase in full-time work versus a 7.3 percent in the sample that qualified for medical marijuana. These results suggest that any decline in productivity resulting from medical marijuana usage -- such as not being able to work at capacity while under treatment -- is outweighed by increased capacity to work.

The study found no evidence that medical marijuana laws were associated with changes in daily activities such as getting dressed, going to the bathroom or walking.

"These findings underscore the close relationship between health policy and labor supply within older adults," says Nicholas. "When we're doing policy evaluations, we have to think not only about whether the policy is changing health outcomes, but also whether it does it in a way that supports labor force participation."

The results can help inform policy decisions about medical marijuana policy and broaden clinical support for additional research on marijuana as an effective medical treatment. This is important, the authors say, because marijuana is still illegal and classified as a schedule 1 drug at the federal level, and there remains limited clinical evidence available to inform medical marijuana policies and treatment options for many patients, especially older adults.

The study was supported by the National Institute on Aging.