Introduction of the Medicare Prescription Drug program (Part D) in 2006 significantly increased older adults’ access to drug coverage, and, University of Iowa researchers have found, improved seniors’ mental health.

While several studies have examined Part D’s impact on prescription drug use, expenditures, and adherence, few have evaluated how these changes have affected seniors’ health—in particular, their mental health. Depression is currently the most common mental illness among older adults.

To address this gap, researchers at the University of Iowa College of Public Health, led by Padmaja Ayyagari, assistant professor of health management and policy, looked at data from the Health and Retirement Study (HRS) and the Medical Expenditure Panel Survey before and after the launch of Part D.

“We wanted to evaluate whether Part D has effects that go beyond the financial protection of seniors, and whether it results in measurable and meaningful improvements in health,” says Ayyagari, who co-authored the paper with Dan Shane, assistant professor of health management and policy. Their findings were recently published in the Journal of Health Economics.

The HRS, a nationally representative, longitudinal study of people over age 50, includes a group of questions about how respondents felt over the past week: depressed, lonely, happy, or sad, if they slept well, and enjoyed life. To gauge the effect of Medicare Part D, the researchers compared data from 2002-2004 HRS with that from 2006-2010, and compared those ages 65–70 (Part D-eligible group) with those 60–64 (comparison group), who were not yet eligible for Medicare.

The study found that the Part D program significantly improved mental health among older adults. Medicare eligible individuals reported fewer depressive symptoms compared to younger cohorts. Implementation of the program lowered the probability of clinical depression by 4–5 percentage points, which represents a 23–29% decline in rates of depression.

The investigators note that this improvement was most likely due to increased use of antidepressant medications. The program reduced barriers to obtaining prescriptions, trying medications until the correct one could be identified, and adhering to treatment protocols by, primarily, lowering out-of-pocket costs.

These findings may have important implications for the changes being introduced by health care reform. Prescription drugs are among the 10 essential health benefits mandated by the Affordable Care Act. According to the UI researchers, “to the extent that our results can be generalized to other populations, our findings suggest that such changes may be successful in decreasing mental health problems.”