The death of actor Robin Williams has been ruled a suicide, with no alcohol or illegal drugs found in his system, the coroner in Marin County, California, said Friday.

The local sheriff's office has released results of a post mortem, showing he had taken medication - but they were in “therapeutic concentrations.”

The actor was found dead in his bedroom at his Tiberon, California home on August 11. Investigators suspected he had taken his own life by hanging. A representative for the actor said he had been “struggling with depression.” He died age 63.

A cellphone taken from the actor’s jeans pocket was turned off. When the coroner turned the phone on he found no messages, emails or texts referencing suicide.

Williams had suffered from depression for years. He had discussed this openly, even joking about his struggle with substance abuse. He was also struggling with the early stages of Parkinson’s disease.

Williams had “a recent increase in paranoia” and was struggling with insomnia and anxiety associated with Parkinson’s, according to the coroner’s report.

The actor was famed as both a comic and dramatic actor, winning an Academy Award for his role in Good Will Hunting.