Susan Williams, the widow of the beloved Robin Williams, is speaking out about her husband’s death in a new interview with People. "It was not depression that killed Robin," Williams tells the publication. "Depression was one of, let’s call it 50 symptoms, and it was a small one." During his final days, the legendary actor and comedian had actually been battling a disease that's often misdiagnosed or missed altogether.

Doctors were reportedly unable to properly diagnose Robin Williams, who had been suffering through symptoms of a “progressive dementia,” until an autopsy revealed he had actually been battling Diffuse Lewy Body (DLB) dementia. Susan is speaking out now in an effort to bring awareness to an often overlooked disease.

"I’ve spent this last year trying to find out what killed Robin," she says. "To understand what we were fighting, what we were in the trenches fighting, and one of the doctors said ‘Robin was very aware that he was losing his mind and there was nothing he could do about it.'" DLB, according to People, is the second most common neurodegenerative dementia after Alzheimer’s. The disease impacts motor function, causes hallucinations, and inspires "fluctuations" in one’s mental status. According to Susan, Robin had started feeling the toll of the disease during the last year before his death.

For more information on the symptoms of DLB, visit here.