People who are depressed are less likely to adhere to medications for their chronic health problems than patients who are not depressed, putting them at increased risk of poor health, according to a new RAND Corporation study.
Researchers found that depressed patients across a wide array of chronic illnesses such as diabetes and heart disease had 76 percent greater odds of being non-adherent with their medications compared to patients who were not depressed. The findings were published online by the Journal of General Internal Medicine.
The study is the largest systematic review to date to look at the role that depression plays in medication adherence among patients in the United States.
"These findings provide the best evidence to date that depression is an important risk factor that may influence whether patients adhere to their medications," said Dr. Walid F. Gellad, the study's senior author and a natural scientist at RAND, a nonprofit research organization. "There are important implications for both patient health and for health care costs.
"Doctors and other providers should periodically ask patients with depression about medication adherence. Also, when treating a patient who is not taking their medication correctly, they should consider the possibility that depression is contributing to the problem."
Poor adherence to prescribed medication is a well-known problem that is associated with higher death rates among people with chronic illnesses. It is also blamed for increasing U.S. health care costs.
Researchers from RAND and the Claremont Graduate School conducted the study by examining past studies that have measured medication adherence. They combined information from 31 studies involving more than 18,000 people -- significantly more than past reviews -to examine the link between medication adherence and depression.
The study is the first to review the association between depression and medication adherence for patients with high blood pressure and high cholesterol. Other conditions examined in the study include coronary heart disease, diabetes and asthma. The link between depression and medication adherence did not vary significantly between the different chronic illnesses, said Gellad, who is also a physician with the VA Pittsburgh Healthcare System.
"The consistent link between depression and nonadherence across all these illnesses underscores the seriousness of the role that depression plays in keeping people from properly managing chronic conditions," said Jerry L. Grenard, the study's lead author and an assistant professor at the Claremont Graduate School. "That consistency also suggests that lessons learned about how to improve medication adherence among depressed patients with one disease may be applied to other chronic conditions."
Researchers say that depression is just one barrier to getting patients to follow medication recommendations. Additional well-documented barriers to medication adherence are dose complexity and patient cost-sharing. Other barriers that may play a role include beliefs about medications, social support, side effects and provider factors.
The study was supported by the Agency for Healthcare Research and Quality and by Mehlman Vogel Castagnetti.
Other authors of the study are Brett A. Munjas, John L. Adams, Marika Suttorp and Margaret Maglione of RAND, and Elizabeth A. McGlynn of Kaiser Permanente.
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