Court documents obtained by TMZ on Tuesday reveal that, while Robin Williams’ August 11 suicide has previously been blamed on the iconic comedian’s depression, another factor made have contributed to his tragic death. Williams was also reportedly suffering from Lewy Body Dementia, and his family believes this form of dementia played a “key factor” in his decision to end his life.

According to the US National Institutes of Heath, Lewy Body Dementia causes abnormal deposits of protein in the brain and results in progressive cognitive decline, visual hallucinations, and often depression. It often accompanies Parkinson’s Disease, which Williams had been suffering from since 2011.

“Some people with LBD are extremely sensitive or may react negatively to certain medications used to treat Alzheimer’s or Parkinson’s in addition to certain over-the-counter medications,” states The Lewy Body Dementia Association, which reports that the disease affects an estimated 1.3 million people in the United States.

Williams was found dead in a bedroom in his Northern California home on Aug. 11, and Sheriff’s officials publicly confirmed he hanged himself with a belt. Susan Schneider, Williams’ wife, reportedly told authorities shortly after her husband’s death that he had been complaining about his medication and the way it made him feel. Sources close to the Williams family are telling TMZ that his dementia was likely the “key factor” that drove him to commit suicide, and the site claims that Williams’ doctors are also agreeing that the disease may have played a major role in his death.