BROOKLYN - Robin Williams’ wife spoke with “Good Morning America” Tuesday, more than one year after her husband's death.

In the interview, Susan Williams claimed depression was not the cause of his death, but instead blamed a form of dementia called Lewy body.

A coroner’s report revealed Williams had the common, yet difficult-to-diagnose condition that may have led to his suicide.

Dr. Joel Sender, chief of geriatrics at St. Barnabas Hospital, says the condition is so similar to Parkinson's disease that it can be easy to miss.

"Doctors may not always be trained to recognize it because it's a bit unusual in its presentation," says Dr. Sender.

Some of the signs of Lewy body dementia include sleepiness, agitation, paranoia and anxiety.

Dr. Sender says one of the biggest tell-tale signs is visual hallucinations.

"Lewy body patients have the distinct feeling that someone or people or animals are near them, are sitting with them or come to visit them," says Dr. Sender.

Like many progressive diseases, the cause of Lewy body is still unknown.