I just saw this today. Maybe it's old news and everybody already knows.
Yes, Robin Williams had a history of struggling with depression. But I didn't realize that an autopsy showed he wasn't struggling with depression when he took his own life.
He had Lewy Body Disease. It was an undiagnosed neurological disease that causes behavioral changes. His autopsy showed a massive proliferation of Lewy bodies throughout his brain. Virtually every neuron in his brain was affected. Lewy bodies are where a normally occurring protein in the brain clumps in an unnatural way and interrupts brain activity. They cause Parkinsons Disease and also Lewy Body Disease. The link above is an article written by Robin's wife, explaining his symptoms and how the diagnosis was missed. I thought it was a good article.
I couldn't help but think of my own cousin with dementia who passed away recently, and also the millions of people with alzheimers. Both are slightly different neurological diseases, but are similar in that they basically turn the brain into swiss cheese.