Researchers looked at two common types of antidepressant medicines in the study. They found that both improved depression.
There has been a lingering suspicion that antidepressants may make the symptoms of Parkinson's worse, but this study may help set aside some of those fears.
"We showed that we have effective and well-tolerated treatments for depression in Parkinson's," says researcher Irene Hegeman Richard, MD, associate professor of neurology and psychiatry at the University of Rochester Medical Center.
"Depression is the thing that most impacts quality of life," she says. "It's present in almost 50% of patients."
About a million people in the U.S. have the brain disorder, according to the National Parkinson's Foundation. It leads to shaking or tremors and difficulty with walking, movement, or coordination.
The study is published in the journal Neurology. It was funded by the National Institutes of Health/National Institute of Neurological Disorders and Stroke and Johns Hopkins University School of Medicine.
Treating Depression in Parkinson's Disease
Depression in people with Parkinson's is still under-recognized and under-treated, Richard tells WebMD.
As doctors have become more aware of how common it is, she says, they have struggled with how best to treat it.
Older antidepressants known as tricyclic antidepressants are sometimes used, she says. But their use is linked with certain types of heart problems and other side effects.
Paroxetine is an SSRI (selective serotonin reuptake inhibitor), which affects levels of the hormone serotonin in the brain, improving mood.
Venlafaxine extended release is an SNRI (serotonin and norepinephrine reuptake inhibitor). It works by balancing the two hormones to improve mood.
The 115 patients all had both Parkinson's and clinical depression. Patients had to be at least 30 years old and free of dementia. They were treated at 20 different centers in the U.S., Canada, and Puerto Rico from June 2005 through March 2009.
The patients were assigned to one of three groups: paroxetine, venlafaxine, or placebo.
The patients took a maximum of 40 milligrams of paroxetine or 225 mg of venlafaxine daily.
The researchers evaluated their depression at the start and throughout the 12-week study. They looked to see if the treatment affected their movement ability.
Treating Depression in Parkinson's Disease: Study Results
Patients in all three treatment groups, including the placebo group, showed improvement on a commonly used scale to gauge depression known as the Hamilton Rating Scale.
Those on antidepressants improved more than did those on placebo, Richard says.
On average, those getting Paxil had a 59% improvement. Those taking Effexor had a 52% improvement. Those who got the placebo had a 32% improvement.
Richard evaluated their depression using three other scales and found similar results.
There was no effect on movement ability.
Richard can't say which antidepressant type is better for treating depression in Parkinson's disease, she says. The study did not do a head-to-head comparison of the two types.
Each type, SSRI and SNRI, includes many different medicines, so patients have a choice, she says.
Both medicines studied are available as generics, Richard says. At the doses studied, the cost would be about $20 to $30 a month.
Patients reported side effects such as insomnia, constipation, sexual dysfunction, and fatigue. Three patients, including one in the placebo group, had serious side effects. These included chest pressure, bowel obstruction, and heart rhythm problems.
However, only the patient with heart rhythm problems withdrew.
Richard reports serving on the scientific advisory board for the Michael J. Fox Foundation. She has received a speaker honorarium from Teva Pharmaceutical Industries and research support from Neurologix, Inc., Eli Lilly and Company, Cornell University, and the Michael J. Fox Foundation.
Wyeth Pharmaceuticals provided the venlafaxine XR. Glaxo SmithKline provided the paroxetine.
Treating Depression in Parkinson's Disease: Perspective
The study has ''critical information" for patients and caregivers, says Michael S. Okun, MD, national medical director of the National Parkinson Foundation. He reviewed the findings.
"The bottom-line message is that treatment for depression in Parkinson's disease matters," he says. "An important aspect of this particular study was that it had a placebo group, and that the investigators showed that either antidepressant performed better than placebo for Parkinson patients."
An editorial that accompanies the study concludes that depression in Parkinson's patients may be as treatable as it is in the general population.