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Mood Disorders Affect Half of Patients Diagnosed with Parkinson's Disease

Parkinson's is a chronic neurological disease that affects an estimated 6.3 million people worldwide. It is marked by tremors and rigidity and problems with walking, posture and speech.

Laura Marsh of Johns Hopkins University Medical School says mood disorders often accompany the physical symptoms. "Depressive disorders are the most common psychiatric disturbance in Parkinson's, and they affect about 50 percent of patients," she says. "Anxiety disorders have received much less attention than depression, but they affect about 25-40 percent of patients."

Dr. Marsh says those rates are greater than what would be expected in the general population of similar age or among people with comparable disability. Patients tell her these emotional disorders have a greater impact on their quality of life than do physical symptoms.

"In particular what you see in Parkinson's patients with mood disorders compared to those who don't [have that] is that they have worse motor deficits," she say. "They have greater cognitive difficulties, and they even have greater physical disability associated with their disease. And, the patients with depression when it is untreated -- research has shown at [Johns] Hopkins and elsewhere -- that they have accelerated disability compared to those who don't have depression."

Dr. Marsh says the good news is that mood disorders are treatable. The bad news is that so few patients take advantage of the care. "Up to 75 percent of [Parkinson's] patients with an active mood disorder are undiagnosed," she says. "Among the minority who are actually diagnosed, at least half of those tend to go untreated or under-treated from the morbidity [sickness] just associated with the mood disorder, not just the Parkinson's disease."

Laura Marsh says because many patients and caregivers are unaware of the connection between Parkinson's and psychiatric disorders, new strategies are needed to detect depression and to treat it.