'Biological basis' for depression in Parkinson's patients: expert

Robin Williams' widow stunned many of his fans Thursday when she announced that not only was her husband suffering from depression and anxiety at the time of his death, he also was in the early stages of Parkinson's Disease.

Experts say Williams' case is not so unusual, as depression and Parkinson's are often linked.

Dr. Michael Okun, the medical director of the National Parkinson Foundation's and a professor of neurology at the University of Florida, says depression among Parkinson's patients has been largely misunderstood until recently.

"We have recently learned that depression in Parkinson's is actually quite common. It occurs in more than half of people with this disease and it is the largest unmet hurdle to treatment," Okun told CTV News Channel from Gainesville, Fla.

Okun says several large studies in recent years have revealed that for many Parkinson's patients, depression is not just a reaction to their diagnosis -- although that does occur. The disease itself can increase the risk of depression, he says.

"We now know there are biological changes in the brain, both from the degenerative process but also because of changes in chemicals such as dopamine, serotonin and norepinephrine. So we now know there is a biological basis for these depressive symptoms," he said.

Dopamine levels drop in people with Parkinson's, which is the primary cause of the tremors and other motor symptoms of the disease. When dopamine drops, so does serotonin, a neurotransmitter that regulates mood and contributes to feelings of happiness.

The Michael J. Fox Foundation says depression needs to be treated when it's discovered because the condition can hinder some of the key elements of Parkinson's treatment, such as staying socially connected and exercising to manage motor symptoms.

Research from the National Parkinson's Foundation has found that people with Parkinsons who are suffering from depression have more trouble with daily activities, and are more likely to begin medication for motor symptoms sooner than those without it. Depression also tends to make Parkinson's symptoms worse, their research has found.

The good news is that depression is highly treatable. Studies have shown antidepressants are effective in those with Parkinsons, boosting serotonin without aggravating motor symptoms. Psychotherapies, such as cognitive-behavioral therapy, can also help some.

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'Biological basis' for depression in Parkinson's patients: expert