People who are depressed may have triple the risk of developing Parkinson's disease, according to a study published in the October 2, 2013, online issue of Neurology, the medical journal of the American Academy of Neurology.
"Depression is linked in other studies to illnesses such as cancer and stroke," said study author Albert C. Yang, MD, PhD, with Taipei Veterans General Hospital in Taipei, Taiwan. "Our study suggests that depression may also be an independent risk factor for Parkinson's disease."
Researchers analyzed the medical records of 4,634 people with depression and 18,544 free of depression over 10 years. They also looked at the risk of Parkinson's disease after excluding people who were diagnosed with Parkinson's disease within two or five years following their depression diagnosis.
During the 10-year follow-up period, 66 people with depression, or 1.42 percent, and 97 without depression, or 0.52 percent, were diagnosed with Parkinson's disease. People with depression were 3.24 times more likely to develop Parkinson's disease than those without depression.
"Many questions remain, including whether depression is an early symptom of Parkinson's disease rather than an independent risk factor for the disease," Yang said. "Our study also found that depression and older age and having difficult-to-treat depression were significant risk factors as well."