For the first time in more than a year, the widow of the actor Robin Williams is speaking publicly about the circumstances that preceded Mr. Williams’s death, and sharing details about a disease he had when he died.

In interviews with People magazine and with ABC News, the widow, Susan Schneider Williams, laid the blame for her husband’s suicide in 2014 not on depression but on diffuse Lewy body dementia.

“It was not depression that killed Robin,” Mrs. Williams said in the People magazine interview. “Depression was one of let’s call it 50 symptoms and it was a small one.”

She added: “This was a very unique case and I pray to God that it will shed some light on Lewy bodies for the millions of people and their loved ones who are suffering with it. Because we didn’t know. He didn’t know.”