Strange behavior like eating or having sex while asleep raised some serious questions about drugs against insomnia such as Sanofi-Aventis' Ambien. Ambien is the most popular prescription sleep medication. Last year, 26.5 million prescriptions filled for drugs including Ambien brought the producing companies $2.2 billion.

Since 2001, these prescriptions have risen by 53% and now about 30 million people in the United States are on sleep medication. Some of the most serious side effects are short-term memory loss and accidents caused by patients who drive the next day still under the influence of drugs.

Donna Arand, president of the American Insomnia Association, stated: "Patients who may have engaged in this unusual behavior at night -- it's relatively rare and bizarre. The daytime sleepiness, that drugged feeling that people may have, is probably the most worrisome because of the (vehicular) accidents that can occur."

"I put on over 100 pounds [~50kg] since I've been on Ambien. I would wake up in the morning and there would be candy wrappers all around the bed. There would be crumbs in the bed. There would be all kinds of evidence that someone had been eating in the bed. But I had absolutely no recollection of it," said Brenda Pobre, a woman who took the drug.

Researchers in Minnesota started examining cases of people behaving strangely in their sleep. Dr. Mark Mahowald, who is currently studying cases related to Ambien, stated: "We've had people eat buttered cigarettes. We've had people make salt sandwiches. It's a release of two innate behaviors, namely sleep and eating and they're both released at the same time by the sleeping medication."