Actor Robin Williams appears onstage during MTV's Total Request Live at the MTV Times Square Studios on April 27, 2006 in New York City. (Photo by Peter Kramer/Getty Images) Robin Williams on April 27, 2006, in New York City. (Peter Kramer/Getty Images)

According to an exclusive report by TMZ, Robin Williams was suffering from Lewy body dementia, and the disease may have contributed to his decision to commit suicide earlier this year.

Here’s how the National Institutes of Health defines “dementia with Lewy bodies”:

The central features of DLB include progressive cognitive decline, “fluctuations” in alertness and attention, visual hallucinations, and parkinsonian motor symptoms, such as slowness of movement, difficulty walking, or rigidity.  People may also suffer from depression.  The symptoms of DLB are caused by the build-up of Lewy bodies – accumulated bits of alpha-synuclein protein — inside the nuclei of neurons in areas of the brain that control particular aspects of memory and motor control. 

Because Williams had battled depression, drug abuse and alcoholism — and had again checked into the Hazelden rehabilitation facility just weeks before his death — it was widely speculated that his depression led him to suicide. His publicist told the media Williams had been battling “severe depression” before his death.

Wrote TMZ:

Robin’s wife had told authorities shortly after his death he had been complaining about the meds and the way they made him feel.

Sources connected with the Williams family tell TMZ … Lewy Body Dementia was the “key factor” they believe drove him to kill himself. We’re told Robin’s doctors agree that the disease was the critical factor leading to his suicide.

Just this spring, the public learned the late Casey Kasem was suffering from Lewy body dementia after the Top 40 king went missing.

From "Mrs. Doubtfire" to "Good Will Hunting," Oscar-winning actor Robin Williams, who died at 63, gave fans decades of memorable moments on screen. The Post's movie critic Ann Hornaday reflects on the actor's unforgettable career and the legacy he leaves behind. (Jhaan Elker/The Washington Post)