By Vincent Richeux

Sexsomnia, a parasomnia characterized by amnestic sexual behavior during sleep, is sometimes invoked as a defense in sexual assault cases.

A forensic expert specializing in sexsomnia, Isabelle Arnulf, MD, PhD, professor of neurology at Sorbonne University, and head of the Sleep Disorders Unit at Pitié-Salpêtrière Hospital, Assistance Publique–Hôpitaux de Paris, Paris, France, presented at the Sleep Congress 2025 in Strasbourg, France, the polysomnographic criteria that support the diagnosis of this still poorly understood disorder.

Performed in a specialized center over two consecutive nights and up to three nights in medicolegal cases, polysomnography can “support the diagnosis of sexsomnia,” particularly when no overt sexual behavior is observed, Arnulf emphasized. Automatic masturbatory or pseudocoital movements occur in nearly half of the cases.

Recognized and described since the early 2000s, sexsomnia is classified as a parasomnia, an unconscious behavior that occurs during sleep. This form of sexual sleepwalking predominantly affects men, accounting for approximately 80% of cases, and manifests as moaning, pelvic thrusting with or without attempted penetration, or episodes of masturbation.

Prevalence is difficult to determine because affected individuals rarely seek care; sexsomnia may not be uncommon.

Not Rare

Episodes generally occur during deep non-rapid eye movement (NREM) sleep (stage N3) immediately before REM sleep. “Sexsomnia may also occur during N2, light NREM sleep, with confused arousal and mumbling.” Evidence of sleep state is frequent because snoring often accompanies unconscious sexual activity.

According to the literature, nearly half of individuals with sexsomnia have another form of parasomnia, most often sleepwalking, night terrors, or sleep talking. Arnulf noted that sexual behavior is “more often disinhibited and more direct” compared with waking sexual activity. Individuals may engage in sexual acts, sometimes without their partner’s consent, while in a sleepwalking state and then wake with no memory or confusion about the episode.

A Norwegian survey of 1002 adults with a mean age of 50.3 years found that 10.5% reported at least one episode of sexsomnia during their lifetime, with 6% reporting an episode in the previous 3 months. A family history of deep sleep parasomnia is a recognized predisposing factor.

Sleep Loss, Stress, Alcohol

Sleep deprivation, stress, and alcohol consumption are major risk factors. On the day preceding an episode, individuals most often reported lack of sleep (53% of cases), stressful situations (35%), and acute alcohol consumption (29%). Sexual frustration was reported by 18% of participants.

While this condition remains taboo, it can also have serious consequences because sexsomnia can lead to allegations of sexual assault or even rape within the family or marriage. Among sleep disorders, sexsomnia is “the most frequently encountered in judicial proceedings,” as Arnulf said.

In 2022, Léo Grasset, the creator of the YouTube DirtyBiology Channel , publicly disclosed his sexsomnia diagnosis in response to multiple rape complaints filed against him. In the medicolegal context, sexsomnia may be invoked to establish a lack of criminal responsibility.

Arnulf regularly provided expert testimonies in court; as a sleep specialist, of the 23 most recent expert assessments, 17 involved potential cases of sexsomnia. Other incidents involved fatal road accidents linked to drowsiness and nighttime violence involving strangulation, possibly related to parasomnia.

In early November, international experts, including Arnulf, convened as think tanks in forensic sleep medicine to agree on the criteria supporting the involvement of sexsomnia in medicolegal settings. Video polysomnography features were among the criteria discussed, she said.

Prevention First

Arnulf and colleagues conducted a study to determine whether polysomnography criteria typically used to characterize parasomnias are present in individuals with sexsomnia. The results showed fragmentation of N3 sleep in approximately half of the patients, slow-wave arousal in two thirds, and at least two eye openings during N3 sleep in nearly half of the patients.

The sensitivity of these criteria was lower than that of the other parasomnias. Sexual behavior during N3 sleep remained common during evaluation. Over two consecutive nights, 4 out of 10 patients with sexsomnia exhibited sexual activity during deep sleep.

Once a diagnosis is established, management primarily relies on prevention. “It is important not to sleep with individuals with whom they are not sexually involved,” Arnulf said. Partners should be informed and advised to wake the person if their behavior is perceived as aggressive.

Prevention also involves reducing risk factors such as fatigue, stress, and alcohol consumption. Good sleep hygiene is essential for maintaining good health.

For pharmacologic treatment, off-label paroxetine, a selective serotonin reuptake inhibitor, may be initiated at one quarter of a 20-mg tablet taken 1 hour before bedtime and gradually increased to three quarters of a tablet during periods of stress. If needed, 100-400 mg/d of gabapentin may be considered as second-line therapy.