Imagine waking up in the morning to hear about your strange behavior from the previous night, but without a hangover.

University prelaw student Charles Carlson knows exactly how it feels to find out what happened but have no idea it did.

“My partner will wake me up to tell me I was humping him or grinding on something,” he said, adding that the experience often causes him to ejaculate during sleep.

Carlson said he also grinds his teeth in his sleep, which his dentist believes to be an erotic fixation.

This type of behavior is more common than once thought, according to a new research paper appearing in the June issue of the journal SLEEP.

The research paper, written by University psychiatry professor Dr. Carlos Schenck and Dr. Mark Mahowald, neurology professor and medical director of the Minnesota Regional Sleep Disorders Center, is the result of an extensive review of sleep disorders. Research led to the classification of a new sleeping disorder, sexsomnia.

Sexsomnia is a disorder in which people exhibit various types of sexual behavior, including moaning, masturbating, sexual talk or even sexual contact with their partner, Schenck said.

This phenomenon is a newly classified form of sleepwalking, because all the actions happen while the person is unconscious and unaware of what is going on.

Sexsomnia is not a new disorder, but the number of cases is rising as people become more aware of it, Schenck said.

The total number of people suffering from this is unknown, because people might be embarrassed to come forward about it, he said.

An increase in sexsomnia cases led both Schenck and his colleague to continue to research this topic.

“We found there were bits and pieces of information and not a comprehensive study on this disorder,” Schenck said.

The two doctors said they wanted to alert the medical community about the disorder, so they researched medical literature about sexual behavior relating to sleep disorders and sexual activity during sleep.

The research included sleep-related disorder cases from across the country, and found sexsomnia mainly affects males.

College students are at a higher risk for developing sexsomnia, since they usually suffer from sleep deprivation – the No. 1 risk factor for all sleep disorders, Schenck said.

While there is no known direct cause of sexsomnia, it is rare for sexsomnia to be the only sleeping disorder a person has. Schenck said in all cases studied, the sexsomniacs exhibited two or three other forms of sleep disorders.

According to the research, there are cases in which men would actually have sex with their partner during the night without knowing it.

One case mentioned in the study involved a 38-year-old man who would have unconscious sexual intercourse with his wife at least once every 15 days for 12 years.

He would rip off her clothes, fondle her and begin intercourse. His wife reported that her husband was “not present” and “unresponsive” and that, one time, he even choked her.

A person suffering from sexsomnia is half-awake, half-asleep and not responsible for his or her behavior, Schenck said.

Psychology sophomore Thomas Rossi said he believes people can do unusual things in their sleep. He said he would probably believe it if a friend had this experience, but it would depend on the friend.

“I would probably laugh at first but then tell them not to sleep with other people if they have experienced this before, to be safe,” Rossi said.

People who suffer from sexsomnia are not sex-deprived or wanting sex. Instead, it is an instinctual action, Schenck said.

“This is a basic instinct, like eating, and not a sign of a psychiatric disorder,” he said.

While this can be a funny topic, it can also be a serious problem. One can be arrested for sexual assault while denying responsibility because he or she was unconscious, Schenck said.

In Toronto, a man was acquitted after being arrested for sexual assault when he claimed sexsomnia as a defense, Schenck said.

Doctors treat sexsomnia with a drug called Clonazepam. This drug raises the arousal threshold and makes it harder for an individual to become aroused, Schenck said.

Sexsomnia happens when an “alarm” goes off in the nervous system. But with this medication, the signal is less likely to go off, allowing the person to remain asleep, he said.

Sexual behavior while sleeping is not always a bad thing. There is a gray area between normal and abnormal sexual behavior, and it is up to individual couples to decide where this area is, Schenck said.

Some couples in the study have stated that their partners are more affectionate while sleeping and do not see it as a problem.

Carlson said he is not currently treating his sexsomnia, because his partner tells him it is not a problem.