WEDNESDAY, April 11 (HealthDay News) -- Some of the newer antidepressants can help treat depression in people with Parkinson's disease without aggravating other disease symptoms such as tremor or rigidity, researchers have found.

Nearly 1 million people in the United States are living with Parkinson's disease, a progressive movement disorder marked by tremor, slowness and/or rigidity. Parkinson's disease and depression tend to travel together, and there has been concern that some of the medications used to treat depression may worsen motor symptoms.

A new study published online April 11 and in the April 17 print issue of Neurology shows that this is not the case, at least when it comes to the antidepressants Paxil (paroxetine) and Effexor (venlafaxine).

Paxil is in the class of drugs known as SSRIs (selective serotonin reuptake inhibitors) while Effexor is an SNRI (serotonin and norepinephrine reuptake inhibitor).

In the new study of 115 people with Parkinson's disease, participants received Paxil, Effexor or an inactive "placebo" pill. The researchers followed-up with patients for 12 weeks and found that both antidepressants improved symptoms of depression without worsening some of the motor symptoms associated with the disease.

On average, those people who took Paxil had a 59 percent improvement and those receiving Effexor had a 52 percent improvement in scores on a standardized tool measuring depression. People who received the placebo had a 32 percent improvement. Three other depression-rating scales showed similar results.

The drugs did not lead to any worsening in motor symptoms, the investigators noted. Use of antidepressants did not improve anxiety levels, thought processes or overall health-related quality of life among the study participants.

Sleep problems were among the most commonly reported side effects. Weight gain was seen with Paxil and at the final study visit, an increase in sitting blood pressure was seen with Effexor, according to the report.

"Depression is the number-one factor negatively affecting the quality of life for people with Parkinson's disease," study author Dr. Irene Hegeman Richard, a neurologist at the University of Rochester Medical Center in Rochester, N.Y., said in a university news release. "It causes a great deal of suffering among patients. The great news here is that it's treatable. And when the depression is treated adequately, many of the other symptoms become much more manageable for patients."

Depression in Parkinson's disease is caused by the underlying disease process, not the stress of dealing with a chronic disease, she said.

Commenting on the study, Dr. Joe Verghese, a neurologist at the Albert Einstein College of Medicine in New York City, said the study provides good news for people with Parkinson's disease and depression. "There is always a concern that we may upset the applecart in Parkinson's by adding a new medication."

Dr. Roy Alcalay, an assistant professor of neurology at Columbia University Medical Center in New York City, agreed that treating depression in Parkinson's disease can be a delicate balance. "The new study validates what we have been doing," he said. "The medications used to treat depression in the general population work as well for Parkinson's disease, and there is no evidence that they have bad side effects on motor symptoms."

While the new study only looked at two antidepressants, "this doesn't mean that others don't work," Alcalay said. As to the robust placebo effect seen in the new study, he said that "just thinking that they are getting treated often helps people with depression."

Treating depression in Parkinson's is important, Alcalay said, and "the study helps us do so in a more educated way."

The U.S. National Institutes of Health/National Institute of Neurological Disorders and Stroke and the Johns Hopkins University School of Medicine funded the study. Wyeth Pharmaceuticals provided Effexor XR and the placebo, while GlaxoSmithKline provided Paxil.

More information

Learn more about Parkinson's disease at the U.S. National Institute of Neurological Disorders and Stroke.