By Brad Edwards

(CBS) – Actor and comedian Robin Williams was privately battling Parkinson’s disease when he took his own life this week, according to his wife.

CS 2’s Brad Edwards says the actor’s well-known struggle with depression and Parkinson’s diagnosis is causing some worry.

Some experts and patients worry: Is there a connection between the disease and suicide?

Dr. Cynthia Comella, a professor of neurology, says the calls have been coming in since the news broke.

Asked if there’s a connection with Parkinson’s and taking one’s own life, Comella responded: “In my clinical experience, the occurrence of suicide associated directly with Parkinson’s disease is very rare.”

“Perhaps Parkinson’s disease was maybe a log on the fire, but I don’t think it was the reason,” she says of Williams.

The disease increases risk of depression. Parkinson’s patient Kelly Weinschreider says she has dealt with both.

“It can get pretty bleak,” she says.

She was once 29 and making good money.

Now on disability, she is the founder of a support group at Rush University Medical Center.

“It’s been a struggle, no doubt, but I think I’m doing really well,” Weinschreider says.

Depression may triple the risk of Parkinson’s disease, especially in elderly.

Brad Edwards