From Wikipedia, the fourth para from top:

During his final years, Williams struggled with severe depression before his death from suicide in 2014 at his Paradise Cay, California, home at age 63. According to his widow, Williams had been diagnosed with Parkinson's disease, and had been experiencing depression, anxiety, and increasing paranoia.

Note the article listed as the source for that statement, and its title: Robin Williams’ widow speaks: Depression didn’t kill my husband. As she eloquently puts it,

Comedian Robin Williams’ widow, Susan Williams, said she and her husband “were living a nightmare” in the months leading up to his death.

“My best friend was sinking,” an emotional Williams told ABC’s Amy Robach in an interview that aired Tuesday, her first since Robin Williams killed himself in August 2014.

Williams said she’s spent the last year trying to get to the bottom of what led him to take his own life. Contrary to what most people think, she said, it wasn’t depression, nor was it a re-emergence of his longtime struggles with alcohol and drug addiction.

She never said her husband had no depression; quite the contrary. What she said was that depression didn't kill him.

Neurological disorders (such as various forms of dementia) and depression go hand in hand; it could even be said that clinical depression, being a dysregulation of the neurotransmitters that control mood, is a neurological disorder itself.

I don't want to get into the weeds with the medical nomenclature of depression, just because there has rarely been a time when it was not disputed. But the lived experience of dementia and its frequent accompanying depression can't be separated. You're just demonstrating your lack of knowledge of both and, it could be added, a serious lack of compassion here.

EDITED to add link