Parasomnias: Types, Symptoms, & Causes

There are different types of parasomnia, and each parasomnia carries distinct symptoms and diagnostic criteria. These behaviors can be categorized into sleep stages: NREM-related, REM-related, and “other.”

NREM-Related Parasomnias

Non-REM sleep includes light and deep sleep, accounting for about the majority of your sleeping time, approximately 75% of the sleep. It encompasses three sleep stages in the following order: N1, N2, and N3.

Non REM parasomnia is a disorder with mysterious neurobiological substrates. The conditions are severe, with social, personal, and forensic implications. Non REM parasomnia can be triggered by factors causing an increase in deep sleep (sleep deprivation) or sleep disruption (stress), and symptoms vary over time.

It encompasses unwanted night-time disorders of arousal (DOAs) such as sleepwalking, sleep terrors, and confusional arousals, which are thought to be due to incomplete awakening from deep NREM sleep, as well as lesser-known entities such as sleep-related sexual behaviors and eating disorders.

Sleepwalking

Sleepwalking is thought to be a common arousal disorder characterized by partial arousal during non-REM sleep. Sleepwalking can lead to potential adverse health outcomes, such as injury to the sleepwalker or others due to impaired perception. And according to study reports, the current rate of sleepwalking is higher in children than in adults.

Sleep Terrors

Sleep terrors are early childhood parasomnia. Screams or cries, behavioral manifestations of extreme fear, difficulty waking, and inconsolability upon awakening characterize them. Although research has demonstrated that night terrors are most common in children between 1 and 5 years of age.

Confusional Arousals

Confusional arousal is considered as parasomnia, which refers to when a sleeper appears to wake up, but their behavior is unusual or strange. The individual may feel disoriented, unresponsive, have slow speech, or confused thinking, such as not knowing where they are or what they are doing. Furthermore, confusional arousals are highly prevalent in the general population.

Sleep-related Sexual Behaviors

Sleep-related abnormal sexual behaviors, also known as sexsomnia, are classified as a subtype of non REM parasomnia. It can be associated with other sleep disorders, such as restless legs syndrome and obstructive sleep apnea (OSA), which promote arousal from NREM sleep with partial awakening. Individuals with sexsomnia perform sexual activities while asleep. 

Sleep-related Eating Disorders

Sleep-related eating disorder (SRED) is a combination of parasomnia and an eating disorder characterized by recurring eating events during the transition from night-time sleep to arousal. It is associated with psychotropic medication, particularly sedative-hypnotics, including parasomnias, narcolepsy, and restless legs syndrome.

REM-Related Parasomnias

Rapid eye movement (REM) sleep occurs following the NREM stages. And in human adults, REM sleep was correlated with specific brain-wave patterns and dreaming occurred during periods of sleep with rapid eye movements. It is also when nightmares can occur.

REM sleep accounts for about 25% of sleep and usually starts 90 minutes after the sleep, and later each of the REM cycles gets longer throughout the night. The first cycle generally lasts 10 minutes, with the final cycle lasting up to an hour.

The REM-associated parasomnias include nightmares, REM-sleep behavior disorder, and hypnagogic and hypnopompic hallucinations.

REM-Sleep Behavior Disorder

One of the cardinal features of REM sleep is the active inhibition of skeletal muscle during REM sleep. And REM-sleep behavior disorder is a sleep disorder in which the sleeper physically acts out vivid and often unpleasant dreams with vocal sounds. It may sometimes include sudden and often violent arm and leg movements during REM sleep. This behavior is also called dream-enacting behavior.

Nightmares

A nightmare is a disturbing dream associated with negative feelings, such as anxiety or fear, that awaken the sleeper from REM sleep. Dream content most frequently involves imminent danger; attacks or pursuit are common themes, with fear and/or anxiety being the most frequent emotions associated with nightmares. Sometimes sadness, anger, and dysphoria may also be included. 

Contrary to sleep terrors, which may evolve into sleepwalking, nightmares are not associated with confusion or disorientation. The individual having a nightmare can relate dream content and associated fear and anxiety upon awakening.

Hypnagogic and Hypnopompic Hallucinations

Hypnagogic hallucinations are vivid perceptual experiences occurring at the onset of sleep, and hallucination upon awakening is called hypnopompic. The hallucinations can be pleasing or frightening and are often visual, but they can be auditory, tactile, or cenesthopathic (abnormal sensations).

Other Parasomnias

Behaviors that occur during the transition between sleep or wakefulness, as well as those that can occur during NREM or REM sleep, is parasomnia definition. 

Exploding Head Syndrome

Exploding head syndrome (EHS) is a benign parasomnia. It is characterized by the perception of a loud sound while asleep, which leads to abrupt awakening. It usually occurs during the wake-sleep/sleep-wake transition, lasts less than a second, and is often accompanied by flashes of light and patient distress, but there is no significant associated pain.

Sleep Enuresis

Sleep enuresis or nocturnal enuresis is known as bedwetting worldwide. It is defined as night-time bedwetting in children five years or older and is a common condition that can cause substantial psychological distress in children. Moreover, there are three commonly proposed mechanisms for bedwetting: excessive nocturnal urine production, bladder overactivity, and a failure to awaken in response to bladder sensations.