Chocolate could be aggravating the sleep disorder which causes sufferers to act out violent nightmares, according to scientists in a recent New Scientist report.
The disorder, called rapid eye movement sleep behaviour disorder (RBD), affects around one in 200 people, and is more commonly experienced by men. Those affected are said to thrash about while sleeping and shout as they dream.
Robert Vorona of the Sentara Norfolk General Hospital in Norfolk, Virginia, the study leader, said that the caffeine in chocolate blocks the normal atonia process, which paralyses people during dreams, and the sleeper is more likely to move.
Vorona reports on a case-study in which the sleeping behaviour of one man was directly affected by what he had eaten previously. The man, who lashed out in his sleep during recurrent nightmares, experienced the problems after eating chocolate biscuits, ice cream or syrup.
While the symptoms were found to be a result of a former head injury in a car accident, chocolate appeared to make the problems much worse.
Dr Vorona said: "Far be it from me to say chocolate caused the problem. All it probably did was exacerbate it. I admit this is just a case report, but I still think it's interesting."
However Maurice Ohayon of the Sleep Disorders Center at Stanford University, California, told BBC Online that there was no evidence linking chocolate to violent sleep patterns in the general public.
"There's no cause for panic or to stop eating good chocolate," he said.
Dr Mark Blagrove, a sleep and dreaming expert from University of Wales, Swansea, told the news service of the different possible causes for the findings.
"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."
Meanwhile scientists have confirmed there is no evidence to suggest that chocolate could bring on violent sleep patterns in the general population.