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.
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.