The widow of late actor Robin Williams has opened up to reporters about her husband’s suicide last August, and she says that depression wasn’t the culprit.

Robin Williams had been diagnosed with Parkinson’s disease a little over a year before he decided to take his own life. According to his wife, Susan Williams (née Schneider), the actor was suffering from Lewy body dementia, which is often comorbid with Parkinson’s disease and other brain disorders.

After Williams’s suicide, rumors swirled about why the funnyman had killed himself. But his wife told ABC in an exclusive interview that it wasn’t depression, which most people blamed, nor was it a resurgence of Williams’s former drug and alcohol addiction.

In fact, the actor, who was a Chicago native, had been sober for eight years, and his autopsy revealed neither drugs nor alcohol in his system.

Lewy body dementia, also called dementia with Lewy bodies (DLB), can change one’s thinking and reasoning. According to the Alzheimer’s Association, it can also cause alternating confusion and alertness, visual hallucinations, delusions, trouble interpreting visual information, and nervous system malfunctions.

All of these issues occur when the disease begins killing the outer and mid-layer brain cells and distorts the surviving cells in brain structures known as “Lewy bodies,” reports Mic.com.

Many people already experience trouble sleeping at night. Research shows that lying awake for periods of 15 to 20 minutes or more can prolong sleeplessness and lead to problems like insomnia. DLB has even more serious consequences than dragging the next day due to lack of sleep. The Alzheimer’s Association explains that patients who suffer from this condition are also prone to acting out dreams, sometimes violently, as the result of rapid eye movement (REM) sleep disorder.

Memory problems and Parkinson’s symptoms are can also occur with DLB, the latter of which can have debilitating effects and impair movement.

As for Williams, shortly before his death he had been experiencing severe stomach pains and digestive problems along with sleeplessness, said his wife.

The numerous symptoms of DLB resulted in her husband’s death, said Susan Williams.

“It was not depression that killed Robin,” she told People magazine. “Depression was one of let’s call it 50 symptoms and it was a small one.”