Parasomnias

Parasomnias are a group of sleep disorders involving abnormal, undesired physical events or experiences occurring during sleep, sleep transitions, or arousal from sleep. They differ fundamentally from insomnia in that the primary problem is not difficulty sleeping but rather abnormal behaviors or experiences during sleep itself. Key types include NREM sleep arousal disorders (sleepwalking, sleep terrors) and REM-related disorders (REM Sleep Behavior Disorder, Nightmare Disorder), each with distinct mechanisms, timing, and clinical significance.

Parasomnias are grouped broadly into NREM sleep arousal disorders — recurrent episodes of incomplete awakening, usually during the first third of the major sleep period, involving either sleepwalking or sleep terrors, with little dream recall and typically amnesia for the episode — and REM-related parasomnias, including REM Sleep Behavior Disorder (physically acting out dreams due to loss of normal sleep paralysis) and Nightmare Disorder (repeated, well-remembered, distressing dreams). Diagnosis requires the episodes to cause distress or impairment and not be attributable to a substance or another medical condition.

NREM parasomnias (sleepwalking, sleep terrors) have a strong genetic and familial component, and are triggered or worsened by sleep deprivation, irregular sleep schedules, fever, certain medications, alcohol, and stress — all of which disrupt normal sleep architecture and lower the threshold for arousal disorders. REM Sleep Behavior Disorder results from loss of the normal muscle paralysis that occurs during REM sleep, allowing a person to physically act out dream content; notably, it is strongly associated with, and can be an early warning sign of, later neurodegenerative disease (Parkinson's disease, Lewy body dementia), sometimes appearing years before other symptoms.

• Family history of parasomnias, especially for sleepwalking and sleep terrors
• Sleep deprivation and irregular sleep schedules
• Fever, especially in children
• Certain medications, including some antidepressants and sedative-hypnotics
• Alcohol use
• Obstructive sleep apnea, which can trigger arousal-related parasomnias
• Older age and male sex, for REM Sleep Behavior Disorder specifically
• Certain neurodegenerative conditions or their prodromal (early) phase

NREM parasomnias reflect an incomplete transition between deep non-REM sleep and wakefulness — motor behavior and some brainwave patterns appear wake-like while regions governing conscious awareness and memory formation remain in a sleep-like state, explaining the characteristic blank, unresponsive presentation and subsequent amnesia. REM Sleep Behavior Disorder reflects loss of brainstem mechanisms, particularly in the pons, that normally produce muscle atonia (paralysis) during REM sleep — this same brainstem dysfunction overlaps with early neurodegeneration in Parkinson's-spectrum conditions, explaining RBD's significance as a prodromal marker.

• Sleepwalking: rising from bed and walking with a blank, unresponsive expression, sometimes performing complex behaviors, difficult to awaken, no memory of the episode
• Sleep terrors: abrupt arousal with a panicked scream, intense autonomic activation (rapid heart rate, sweating), relative unresponsiveness to comforting, little to no memory afterward
• REM Sleep Behavior Disorder: physically acting out dreams, sometimes with vivid or violent content, potentially causing injury to self or a bed partner, occurring in the second half of the night with clear dream recall on awakening
• Nightmare Disorder: repeated, well-remembered, extremely distressing dreams, usually involving threats to survival or security, with rapid full alertness on awakening

• Recurrent episodes of the specific abnormal sleep behavior or experience (varies by subtype)
• Causes distress or impairment
• Not attributable to a substance or another medical condition
• For suspected REM Sleep Behavior Disorder, co-occurring or emerging neurodegenerative disease should specifically be considered

Conditions a psychiatrist will consider and rule out before confirming this diagnosis:

Nocturnal seizures/epilepsy

Can mimic parasomnias but typically show more stereotyped, repetitive movements; video-EEG monitoring can help distinguish the two.

Nightmares vs. sleep terrors

Sleep terrors occur in NREM sleep early in the night with amnesia and unresponsiveness, while nightmares occur in REM sleep later in the night with full recall and rapid alertness.

Obstructive Sleep Apnea

Can trigger confusional arousals resembling parasomnias, so should be screened for and treated if present.

Panic attacks during sleep

Differentiated by full alertness and clear anxiety-symptom recall, unlike NREM parasomnias.

• Detailed sleep history, including observation from a bed partner or family member, given the person's own amnesia for NREM parasomnia episodes
• Video-polysomnography, particularly important for suspected REM Sleep Behavior Disorder and to exclude nocturnal seizures
• Screening for triggers: sleep deprivation, alcohol, medications, sleep apnea
• Neurological evaluation for suspected REM Sleep Behavior Disorder, given its association with Parkinson's disease and Lewy body dementia

For NREM parasomnias (sleepwalking, sleep terrors), treatment primarily addresses triggers — ensuring adequate sleep, treating sleep apnea, reducing alcohol — and ensuring a safe sleep environment. For REM Sleep Behavior Disorder, melatonin or clonazepam are the primary evidence-based treatments, alongside environmental safety modifications. For Nightmare Disorder, Image Rehearsal Therapy has strong evidence, and prazosin is used specifically for trauma-related nightmares.

Melatonin

A primary, well-tolerated treatment specifically for REM Sleep Behavior Disorder.

Clonazepam

An effective treatment for REM Sleep Behavior Disorder, used alongside safety precautions.

Prazosin

Specifically for trauma-related Nightmare Disorder.

Image Rehearsal Therapy

Specifically for Nightmare Disorder, involving rehearsing a revised, non-threatening version of the recurring nightmare while awake.

Sleep hygiene and trigger-reduction counseling

Addresses precipitants of NREM parasomnias more broadly.

Safety planning and environmental modification counseling

Especially important for REM Sleep Behavior Disorder, given the risk of injury during dream-enactment behaviors.

• Prioritize adequate, consistent sleep to reduce sleep deprivation as a trigger
• Limit alcohol, particularly close to bedtime
• Create a safe sleep environment — remove sharp objects, secure doors and windows, consider a bed alarm for sleepwalking
• Address any underlying sleep apnea
• For REM Sleep Behavior Disorder, pad sharp furniture edges near the bed and consider a bed-partner safety plan given injury risk

NREM parasomnias in children are usually benign and typically resolve with age as sleep-wake transitions mature, though they can occasionally persist into or first appear in adulthood. REM Sleep Behavior Disorder carries a notably different prognosis given its strong association with later development of Parkinson's disease or related neurodegenerative conditions in a substantial proportion of cases over years to decades, making ongoing neurological follow-up valuable. Nightmare Disorder responds well to Image Rehearsal Therapy in most cases.

• Maintaining good, consistent sleep habits and adequate sleep duration to reduce triggers for NREM parasomnias
• Treating underlying sleep apnea
• Moderating alcohol intake
• Ensuring a safe sleep environment for children with sleepwalking or sleep terrors while the condition typically resolves with age

For sleepwalking or sleep terrors, prioritize safety over trying to fully wake the person — gently guiding them back to bed is usually easier and less distressing than attempting to forcefully wake them mid-episode. Don't expect the person to remember the episode the next morning, and secure the sleep environment with locks, alarms, and clear pathways. For REM Sleep Behavior Disorder specifically, bed partners should be aware of injury risk from dream-enactment behaviors, consider safety modifications, and encourage prompt medical evaluation given the neurological significance of this particular parasomnia. Understand these are involuntary events, not intentional behavior.

1. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 5th Edition, Text Revision (DSM-5-TR).
2. World Health Organization. International Classification of Diseases, 11th Revision (ICD-11).
3. American Academy of Sleep Medicine. International Classification of Sleep Disorders.