The cause of suicide by Robin Williams was his disease called Lewy Body Dementia.
The sources linked to his family and the actor's doctors said that the Williams was suffering from the horrible disease, which was the "key factor" that drove him to kill himself, TMZ.com reported.
Lewy Body Dementia is a condition closely associated with Parkinson's disease, and the people who are troubled by both often face severe side effects from Parkinson's meds. The patients often hallucinate and even converse with the illusions.
After Williams death, his wife had told authorities that he had been complaining about the meds and the way they made him feel, and the documents also show that the comedic actor had been struggling with the disease.