Chocolate linked to nightmares

Chocolate may have exacerbated the sleep disorder

A sleep disorder, in which sufferers unknowingly act out violent nightmares, could be aggravated by chocolate, scientists warn.

Rapid eye movement sleep behaviour disorder, or RBD, affects around one in 200 people, mainly men.

In RBD, sleepers also thrash about and shout as they dream.

But scientists have reassured chocolate and cocoa lovers that there is no evidence linking chocolate to violent sleep patterns in the general population.

There's no cause for panic or to stop eating good chocolate

Maurice Ohayon, Sleep Disorders Center, Stanford University, California

The phenomenon of chocolate-stimulated RBD has been documented by Robert Vorona of the Sentara Norfolk General Hospital in Norfolk, Virginia.

Vorona suggests that the caffeine in chocolate helps to block a natural process called atonia that paralyses people during dreams.

That means the sleeper is more free to move.

He studied one man who lashed out in his sleep during recurrent nightmares, in which he tried to protect his home against intruders.

The outbursts happened whenever he had eaten chocolate biscuits, ice cream or syrup.

Case report

Doctors found the problems had begun after the patient had sustained head injuries in a car accident.

But chocolate appeared to make the symptoms much worse.

He has been successfully with sedatives, but the man's symptoms recur if he eats chocolate.

Dr Vorona said: "Far be it from me to say chocolate caused the problem. All it probably did was exacerbate it.

He added: "I admit this is just a case report, but I still think it's interesting."

But Maurice Ohayon of the Sleep Disorders Center at Stanford University, California, said there was no evidence linking chocolate to violent sleep patterns in the general population.

He added: "There's no cause for panic or to stop eating good chocolate."

Dr Mark Blagrove, a sleep and dreaming expert from University of Wales, Swansea, told BBC News Online there were various possibilities about how it could be happening.

"It could be it's actually acting on the atonia and stopping it. It could be that the caffeine in the chocolate is causing atonia.

"Or it's possible that people have more vivid dreams that get acted out."

The report is published in New Scientist, and is due to appear in the journal Sleep Medicine.