Zombie Sex? On a Whole New Level.

(Space.com)- If you think it’s impossible to have sex while you sleep, think again, according to a new study.

There are at least 11 different sex-related sleep disorders, collectively referred to as “sexsomnia” or “sleepsex,” that affect people who are otherwise psychologically healthy—causing them to unknowingly engage in various sexual activities during the night.

Carlos Schenck, a psychiatrist at the Minnesota Regional Sleep Disorders Center, and his colleagues have studied a number of behavioral disorders associated with sleep.

“Any basic instinct can come out in the context of sleep,” Schenck told LiveScience. “All sorts of things can happen.”

They found that people—mostly men—sometimes masturbate, initiate sex with a partner and reach orgasm during sleep. They usually have no memory of these activities when they wake up, learning about them only if a partner or roommate tells them.