What Is Sexsomnia?

Sexsomnia is a type of parasomnia (unwanted behavior that occurs while falling asleep, during sleep, between sleep stages, or during waking up). Sexsomnia involves a person self-touching, making sexual motions, or seeking sex with another person in the bed without being aware of doing it, and without memory of it the next day.

Some notable facts about sexsomnia include:

  • It is a relatively rare phenomenon, much less common than sleepwalking.
  • It's much more common in males.
  • People who experience sexsomnia also have a history of sleepwalking or other parasomnias, and often have a family history of parasomnias.
  • The person having an episode isn't having a sexual dream while it's happening.
  • Many people are unaware of this condition and it was only added to the Diagnostic and Statistical Manual of Mental Disorders in 2013.
  • People won't wander out of bed to search for a partner, and only have sex with a person who is in bed with them.
  • There are reports that people initiating sex during an episode of sexsomnia are more uninhibited and insistent than when they're awake, and it's often robotic and lacks any passion.

Court Cases Involving Sexsomnia

Sexsomnia has been used as a defense in rape trials in the United Kingdom for the last 15 years, and occasionally in Australia since 2008.

A 48-year-old Australian man named Leonard Spencer entered the bedroom of a 21-year-old guest and raped her. His lawyer argued that Mr. Spencer had no recollection of the rape and was asleep at the time. He was acquitted after the defense called on psychiatrist Lester Walton who explained that the accused may have suffered from a condition called "sleep sex."

As sexsomnia is relatively unknown, many believe that this defense isn't a real condition but a way for rapists to not be prosecuted for crimes, similar to someone using insanity as a defense. One of the problems with this defense is that the state of consciousness of the perpetrator at the time of the attack is unknown. Therefore one of the key aspects of demonstrating that someone may have sexsomnia is by presenting a history of sleepwalking or other parasomnias.

According to the Irish Times, in the UK sexsomnia has become such a regular defense in sexual assault cases that if defendants can prove that they suffer from it, prosecutors won't even bring it to trial.

In 2013 a Manchester man was charged with the rape of his friend. His lawyers hired sleep experts who connected him to electrodes for 2 nights and then monitored a third night of sleep deprivation.

Sexsomnia is considered an "automatism" defense where the accused admits to an act but claims it was carried out without intent or control of their actions.

In the US, sexsomnia has been far less successful as a defense. The Journal of the American Academy of Psychiatry and the Law (JAAPL) published a review where they searched the LexisNexis database (a provider of legal, regulatory and business information, and analytics) for the following terms:

  • sexsomnia (10 cases)
  • sleep sex (8 cases)
  • sleepwalking and rape (86 cases)
  • sleepwalking and sex (109 cases)

Cases that only involved one incident or that didn't have a forensic evaluation were excluded. A total of 8 cases fit their criteria; in all but one case the defendant was found guilty, and the one who was found innocent had to appeal his case in the Supreme Court of Tennessee.

The article in JAAPL states "Despite the sleep expert community's international acceptance of sexsomnia as a legitimate diagnosis, the legal community remains skeptical of criminal defendants who put forth the diagnosis in court. Badawy states, “Testimony about unproven conditions like sexsomnia can be challenged on its validity and lack of acceptance in the general medical community under Frye or Daubert”."

Even if it can be shown that a person engages in sexsomnia, it can't always be proven that sexsomnia occurred during a specific incident. It's also true that though sexsomnia may not show up on polysomnography, it doesn't mean that it didn't occur during an incident. Though sleep studies may have limited use in a trial, sleep experts have developed the following guidelines for forensic sleep assessment:

  1. A history of parasomnias including witnesses such as bed partners and witnesses.
  2. Information on sleep/wake habits as well as the use of prescribed and illegal drugs, herbal products, caffeine, and alcohol.
  3. Information about the person's life leading up to the event (such as a divorce or death in the family).
  4. Complete physical, neurological, and psychiatric evaluations.
  5. A video-polysomnography study to rule out other sleep disorders.

A prosecutor or judge may argue that if a person knows they engage in sexsomnia, as a result, they're culpable for any assaults. It's their responsibility to tell others sleeping in their house and to not put themselves in circumstances where they could attack others.

How Common Is Sexsomnia?

The term 'sexsomnia' was first used by Dr. Colin Shapiro from the University of Toronto in 2003, so this is a relatively new discovery. Many people, including members of the medical community, aren't aware this condition exists. Often when a person tells their partner that they tried to have sex with them last night, and the partner says they have no memory of it, the person who was approached for sex often doesn't believe the initiator. 

For these reasons, it's difficult to know how common this condition is. Many people are ashamed to tell their doctors about their experience, and many believe it's something that only they experience.

Almost 8% of patients referred to the Sleep Research Laboratory at the University Health Network's Toronto Western Hospital reported that they had initiated or taken part in sexual behavior while asleep. As this number relates to people referred to a sleep clinic, the number for the general population is much lower.

Sexsomnia looks to be triggered by sleep deprivation, drugs, stress, alcohol, drugs, sleep apnea, or the presence of a partner in bed. Dr. David Cunnington, Director of the Melbourne Sleep Disorders Center told The Sydney Morning Herald, "We explain to people with sexsomnia and their partners that the behavior is not indicative of people's true feelings and is a form of sleepwalking. Some people sleepwalk, some talk, some eat, and some initiate sex. It is not linked to deep-seated psychological issues, or an indicator of mental illness, it is just a failure of switching on/off all parts of the brain in synchrony on the border of wake and sleep."


The causes of sexsomnia are unknown, and it's believed that there's a genetic component. According to Dr. Matthew Walker, Professor of Neurology at the National Hospital for Neurology and Neurosurgery in London and renowned sleep expert explains that sexsomnia is more likely to occur in the first few hours of the night during deep sleep. This is when the cortex, the part of the brain responsible for thinking, awareness, and planning gets switched off, yet the brain stem, responsible for basic urges like eating or sex, is still functioning. This lower part of the brain is amnesic, meaning that there will be no memory of it. One lawyer defending a client accused of rape told the court, "The engine is running, but there's no driver behind the wheel."


According to the International Society for Sexual Medicine, treatment for sexsomnia may include several different treatments, depending on the suspected trigger.

A physician who specializes in sleep medicine may recommend taking steps to improve sleep hygiene. This often includes sticking to a sleep schedule (going to bed and waking up at the same time every day), reducing stress, having a nightly routine that's calming, and avoiding blue light exposure for a few hours before bed.

If the patient is abusing drugs and alcohol, treatment for substance abuse may be recommended. Alcohol use is discouraged.

As stress can be a trigger, patients may be encouraged to reduce the stress in their lives.

In some cases, antidepressants may be prescribed, and in severe cases, the patient may need to sleep in a separate bed from their partner in a locked room. Special alarms that wake the patient during sexsomnia episodes may also be used.

Additionally, patients may need to participate in therapy to deal with the embarrassment and shame that may occur as a result of sexsomnia. Partners may need to be involved if these incidents have caused problems in their relationship.