FRIDAY, June 1 (HealthDay News) -- After uncovering the secret lives of people who walk, eat and become aggressive while asleep, scientists are now turning to another bedtime phenomenon: "sleepsex."
Reports of sexual behavior while asleep have become so common that experts on Friday released a classification system that allows doctors to better document these cases.
People who engage in sleepsex "don't remember what they do, and it's their bed partners who tell them. They're mortified, and the partner complains they're being assaulted or molested," said Dr. Carlos Schenck, a sleep researcher who was lead author on the report. "Now they'll realize this is a sleep-related disorder."
Since the 1990s, researchers have been exploring the range of "parasomnia" behaviors in which people do things other than sleep while sleeping.
Sleepwalking, of course, is nothing new -- ask Lady Macbeth -- but researchers are discovering that people eat while asleep, engage in violence, and even intensely scratch themselves.
"Anything that people do during the daytime, we're realizing they can do during sleep, all the instinctual or basic behaviors," Schenck, an associate professor of psychiatry at the University of Minnesota Medical School, said.
Schenck and colleagues explored existing reports of sexual behavior during sleep and created the classification system. Their work appears in the June issue of the journal Sleep.
The researchers looked at 31 cases of sleep-related sexual behavior. They found that 80 percent involved men. Only males engaged in sleep sexual intercourse (42 percent of cases) while females were more likely to engage in "sexual vocalizations." People of both genders reported incidents of sleep masturbation.
In one case, they reported, "a 28-year-old woman had nightly sexual moaning and sexual fondling during sleep for 16 years that would appear within 20 minutes of falling asleep and disturb the sleep of her husband and children."
In another case, a 26-year-old woman would initiate foreplay with her bed partner during sleep and then awaken and accuse him of forcing sex upon her.
None of the patients reported remembering the incidents.
Patients who have sex while asleep typically do not have any form of mental disorders, Schenck said. "Basically, an alarm rings in their nervous system when it shouldn't ring, and they have this partial awakening. It's a twilight state," he said.
Unfortunately for the patients, "they have suspended judgment," Schenck said. "They can't monitor themselves, and they're are risk for harming themselves or someone else."
In many cases, he added, bed partners reported unwanted sexual advances by a sleeping person, but sometime said they didn't mind the extra attention.
The sedative clonazepam (Klonopin) is a frequent treatment for unwanted behaviors during sleep and it works in 90 percent of parasomnia cases, according to the new report.
It's not clear how common sleepsex is. Dr. Robert Vorona, a sleep researcher and associate professor of internal medicine at Eastern Virginia Medical School, suspects that the true number of cases is not on the rise.
"However, until sleep specialists actively question our patients about these delicate issues, we will not really know just how common or uncommon these behaviors might be, or whether these activities might be occurring more frequently," he said.