FRIDAY, April 27, 2007 (HealthDay News) -- In some cases, depression can be an early manifestation of Parkinson's disease, new research suggests.
Researchers at the Harvard School of Public Health compared antidepressant use among more than 1,000 individuals with Parkinson's disease to more than 6,600 age- and gender-matched individuals without the degenerative neurological illness.
They found that people currently on antidepressants had an 80 percent higher risk of developing Parkinson's disease than those who had never taken antidepressants. This was true for both men and women, regardless of age or the class of antidepressant used.
"We think this is not actually the medication that is causing Parkinson's disease. Instead, we think people who are going to get Parkinson's disease get depression first," said study co-author Dr. Alvaro Alonso, a research associate at Harvard. "It's very important not to say that people taking antidepressants have a higher risk of developing Parkinson's disease," he said.
That's because the effect was only apparent in the year prior to disease diagnosis, and because it was true for two different types of medications, tricyclic antidepressants and selective serotonin reuptake inhibitors (SSRIs), which work via wholly different mechanisms, Alonso explained.
He noted that additional data, not included in the published study, indicated that newer users of antidepressants -- those who had been on the drugs for less than one year -- had a threefold higher risk of developing Parkinson's than people who had never used antidepressants.
Alonso's interpretation: Depressive symptoms could be one of the first manifestations of Parkinson's disease.
The research is scheduled to be presented May 1 at the annual meeting of the American Academy of Neurology, in Boston.
Dr. Rajesh Pahwa, director of the Parkinson Disease and Movement Disorder Center at the University of Kansas Medical Center, in Kansas City, called the observation "interesting."
At the same time, he said, the depression-Parkinson's link is "common knowledge" among neurologists, who have long recognized that depression often occurs alongside Parkinson's disease.
However, primary care physicians and psychiatrists, who may not be aware of the link, "need to pay more attention to this issue," Pahwa said. At-risk individuals who suddenly develop depressive symptoms could in fact be showing the first signs of Parkinson's.
Neurologists could also benefit from these findings, Pahwa added.
"For us, the biggest issue is that we need to pay more attention to depression in Parkinson's disease," Pahwa said. Too often, physicians may view depression as a natural psychological reaction to a Parkinson's diagnosis. However, that may not sometimes be the case, "and we need to treat it more aggressively," he said.
According to Pahwa, Parkinson's disease is a progressive neurodegenerative disorder marked by the loss of dopamine-producing neurons in the brain. Though most commonly associated with motor deficits such as tremors and stiffness, there also are non-motor features, including urinary problems, constipation, insomnia, depression, anxiety, and dementia. There is no laboratory test for Parkinson's, so it must be diagnosed clinically. Nor is there yet any cure for this degenerative disease.
According to the National Parkinson Foundation, 1.5 million Americans currently have the illness, which strikes men and women in roughly equal numbers, usually after the age of 65.
Dr. Giselle Petzinger, a movement disorder specialist at the University of Southern California, said this study is the first to "really suggest" that non-motor features could be early indicators of Parkinson's disease.
"This is pretty convincing data," she said. "Mood probably could be an early manifestation. That's never been shown before."
Petzinger said such early symptoms could enable eventual earlier -- and thus, more effective -- use of neuroprotective medicines, though she noted that no such drug currently exists.
"You want to catch them before they develop motor symptoms," Petzinger said. "That might be a point of no return. Early recognition, that's when you want to capture people."
For more information on Parkinson's disease, visit the National Parkinson Foundation.