Robin Williams may have taken his life due to hallucinations caused by Lewy Body Dementia

Robin Williams may have taken his life after falling victim to hallucinations associated with dementia and Parkinson’s disease, his family are said to believe.

The TMZ website reported that it had obtained documents showing that the comedian, who commit suicide in August, was suffering from a form of dementia called Lewy Body Dementia (or LBD) when he died.

Discovered only in the 1990s, Lewy Body Dementia causes abnormal deposits of protein across the brain, leading to a diminishing of the chemical needed to process normal thinking and behaviour.

It often accompanies Parkinson’s Disease, the neurological condition which Williams had been suffering from for about three years before his death, and was said to be distressed about.

People with Lewy Body Dementia can respond adversely to medications commonly taken for Parkinson’s, and may experience hallucinations in which they see phantom objects, people and animals. It is common for sufferers to attempt to speak to the phantoms.

The Lewy Body Dementia website warns: “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.”

According to the Coroner’s report, Williams had two antidepressants and two caffeine compounds in his system when he died.

A source said by TMZ to be connected with the Williams family told the website that he had complained to his wife, Susan Schneider, about the way his medication made his feel.

The family is said to believe that Lewy Body Dementia was the “key factor” behind Williams’ decision to take his own life at the age of 63.

TMZ said Williams’ doctors agreed that the disease, which affects around 1.3 million people in the United States, was the trigger for his suicide.

It is unclear whether the Good Morning Vietnam star or his doctors were aware of his condition before his death.

According to the Coroner’s report, the much-loved comedian and Oscar-winning actor, who left three children, was suffering from anxiety, depression and paranoia in the run-up to his death on August 11.

He hanged himself in his home in Marin County, California.

His wife told the coroner that the couple had been sleeping in separate bedrooms as he had difficulty sleeping and was often restless at night.

Sleeping issues are a common symptom of Lewy Body Dementia, according to the Association’s website, as are hallucinations, fainting and falls.

As many as half of sufferers will react adversely to medications used to treat Parkinson’s.

Meanwhile, it has emerged that Williams left the bulk of his £30 million fortune to his three children, with provision made for Schneider.

The late comedian’s will states that his children Zachary, 31, Zelda, 25, and Cody, 22, will continue to benefit from a trust he established during his lifetime, with payments made when they reach key milestones in their lives.

Schneider is cared for under the terms of a separate pre-nuptial agreement, which the couple signed a month before their wedding in October 2011.

Williams was worth an estimated $50 million (£31.4 million) when he died, having paid out around $30 million in divorce settlements to his first two wives, the mothers of his children.

He established the Robin Williams Trust in 2009, during his divorce from second wife Marsha Garces, with the stipulation that it pay one-third of the principle to his children when they reached their 21st birthday, with half of the remaining sum being paid out when they turned 25 and the remainder at age 30.

Under the terms of the will, the Trust will now come under the control of a trustee, who will continue to distribute the money as planned.

The will, which was obtained by Mail Online and was filed in Marin County Court last week, also says that Schneider will be cared for under the terms of the pre-nup agreement, which have not been disclosed.

It reads: “I direct the Executor of this Will and the Trustee of the Trust...to fulfill my obligations under that certain prenuptial agreement with Susan dated September 28, 2011.”