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fter Robin Williams killed himself last year, most people, including the actor’s own family, pinned the blame for the suicide on depression. But Williams’ widow is now pointing to a different culprit.

“Lewy body dementia killed Robin,” Susan Williams said in several interviews Tuesday.

Neurologists can’t say for certain what compelled Williams to take his own life, but most medical experts say dementia is an unlikely cause. STAT takes a look at the science:

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What is Lewy body dementia?

LBD is a disease caused by protein deposits in the brain, known as Lewy bodies, that impact thinking, behavior, sleep, and movement. It is the second most common form of dementia after Alzheimer’s disease, affecting an estimated 1.3 million Americans.

“You’re dealing with disease that’s very, very common, but not a whole lot of people know much about it,” said Dr. James E. Galvin, a neurologist at Florida Atlantic University.

Why is it so unknown?

Doctors only recognized LBD as a distinct disease about 20 years ago, and it remains something of a mystery. Researchers like Galvin continue to study the problem. However, funding is an issue.

Last year, while the National Institutes of Health spent $140 million on research for Parkinson’s disease and close to $600 million on Alzheimer’s, the agency only invested $15 million on LBD.

How is Lewy body dementia different from Parkinson’s disease?

Lewy bodies are hallmarks of both diseases, but the earliest symptoms differ.

In Parkinson’s disease, the abnormal protein clumps usually start in lower parts of the brain, causing tremors, rigidity, and other problems of motor control. The dementia only comes later when the Lewy bodies spread. By comparison, LBD starts with protein aggregates in the brain’s largest region, the cerebral cortex, triggering cognitive deterioration from the get-go.

“They’re two ends of the same stick,” said Galvin, “and Lewy bodies are the common theme.”

Is there a link between LBD and suicide?

Most people with LBD experience hallucinations, often seeing children, little people, or animals. But these do not lead to behaviors such as self-injury.

“Depression is probably the most common psychiatric complication,” said Dr. Brent Forester, a geriatric psychiatrist at McLean Hospital in Belmont, Mass. “And it’s most likely directly related to the biological brain changes that occur in patients with the disease.”

The depression caused by the altered brain chemistry can lead people to self-harm. But as Dr. David Knopman, a neurologist at the Mayo Clinic in Minnesota, points out: “Suicide is an extremely uncommon outcome of dementia with Lewy bodies.”

How is LBD treated?

“There’s no one particular drug for the underlying disease,” said Knopman. Rather, each of the various symptoms is managed with a different agent. The cognitive decline might be treated with an Alzheimer’s medicine, the movement problems with a Parkinson’s drug, the hallucinations with an antipsychotic, and so on.

But all these various medicines come with side effects that can interact with each other and exacerbate other symptoms. “The pharmacological management of these patients is really challenging,” said Forester.

Are there new drugs in development for LBD?

Not many. But just this week, a company called Axovant Sciences announced it had acquired the rights to an experimental agent called nelotanserin, which modulates serotonin, the neurotransmitter in the brain that is believed to affect mood. Together with Galvin and other neurologists, the company plans to run clinical trials testing this and other new drugs in patients with LBD.

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  • Anyone facing dementia, with any knowledge of what’s ahead, would contemplate suicide. He was a smart guy and recognized his deterioration. My mother died from a dementia; a rare form that first erodes the victim to comprehend language. One of the last things she scribbled on a paper was, “Me suicide”. She didn’t… and subsequently suffered through eight years of becoming a vegetable before passing on

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