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Carlos H. Schenck

and Mark W. Mahowald

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date: 01 July 2022

Parasomnias are defined as undesirable physical and/or experiential phenomena accompanying sleep that involve skeletal muscle activity (movements, behaviours), autonomic nervous system changes, and/or emotional-perceptual events. Parasomnias can emerge during entry into sleep, within sleep, or during arousals from any stage of sleep; therefore, all of sleep carries a vulnerability for parasomnias. Parasomnias can be objectively diagnosed by means of polysomnography (i.e. the physiologic monitoring of sleep—figures,, and can be successfully treated in the majority of cases. Understanding of the parasomnias, based on polysomnographic documentation, has expanded greatly over the past two decades, as new disorders have been identified, and as known disorders have been recognized to occur more frequently, across a broader age group, and with more serious consequences than previously understood. Parasomnias demonstrate how our instinctual behaviours, such as locomotion, feeding, sex, and aggression, can be released during sleep, itself a basic instinct. There are at least eight reasons why parasomnias should be of interest and importance to psychiatrists: 1 Parasomnias can be misdiagnosed and inappropriately treated as a psychiatric disorder. 2 Parasomnias can be a direct manifestation of a psychiatric disorder, e.g. dissociative disorder, nocturnal bulimia nervosa. 3 The emergence and/or recurrence of a parasomnia can be triggered by stress. 4 Psychotropic medications can induce the initial emergence of a parasomnia, or aggravate a preexisting parasomnia. 5 Parasomnias can cause psychological distress or can induce or reactivate a psychiatric disorder in the patient or bed partner on account of repeated loss of self-control during sleep and sleep-related injuries. 6 Familiarity with the parasomnias will allow psychiatrists to be more fully aware of the various medical and neuro-logical disorders, and their therapies, that can be associated with disturbed (sleep-related) behaviour and disturbed dreaming. 7 Parasomnias present a special opportunity for interlinking animal basic science research (including parasomnia animal models) with human (sleep) behavioural disorders. 8 Parasomnias carry forensic implications, as exemplified by the newly-recognized entity of ‘Parasomnia Pseudo-suicide.’ Also, psychiatrists are often asked to render an expert opinion in medicolegal cases pertaining to sleep-related violence.

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