Parasomnias are a group of sleep-related disorders in which abnormal movements, behaviors, emotions, perceptions or dreams occur during sleep or during transitions between sleep stages. They interrupt normal sleep architecture and can cause distress, injury or impaired daytime function. For a general introduction to sleep-related disorders see sleep disorders resources.

Major categories and examples

  • NREM-related arousal disorders — occur during non-rapid eye movement sleep and often in the first part of the night. Typical examples include sleepwalking, characterized by complex, often repetitive activity while not fully awake, and night terrors, which involve sudden intense fear, crying or thrashing with limited recall.
  • REM-related experiences — happen during rapid eye movement sleep or upon waking. Well-known forms are nightmares, vivid frightening dreams that awaken the sleeper, and sleep paralysis, a temporary inability to move or speak when falling asleep or upon awakening.
  • Other parasomnias — include hypnagogic or hypnopompic hallucinations at sleep boundaries and sleep-related eating disorders (SRED), where individuals consume food with little or no memory of the event.

These categories overlap in some cases and individual experiences vary. Parasomnias may be isolated events or recurrent patterns that affect quality of life.

Causes and risk factors

Parasomnias arise from interactions among genetic predisposition, brain development and triggering factors. Common contributors include sleep deprivation, irregular sleep schedules, stress, alcohol or certain medications, and coexisting sleep problems such as obstructive sleep apnea. Children more often display NREM arousal disorders and may outgrow them; REM-related parasomnias and certain complex behaviours are more frequent or persistent in adults.

Diagnosis and evaluation

Evaluation begins with a detailed clinical history, eyewitness reports and a sleep diary. When the presentation is complex, or injury, unusual behavior or possible seizures are suspected, clinicians may order overnight polysomnography or video monitoring to record sleep stages and abnormal events. Accurate diagnosis distinguishes parasomnias from epilepsy, movement disorders and psychiatric conditions.

Treatment and practical management

Most care focuses on safety, reducing triggers and improving sleep hygiene. Practical measures include creating a safe sleep environment, avoiding sleep deprivation and limiting alcohol. Behavioral therapies—such as scheduled awakenings for predictable NREM events and cognitive approaches for nightmares—are effective for many patients. In selected cases, short-term pharmacologic therapies or targeted treatments for underlying disorders are used under medical supervision. For PTSD-related nightmares, imagery rehearsal and other psychotherapies may be recommended.

When parasomnias cause injury, persistent daytime impairment, or unusual/violent behaviors, seek medical assessment. Reliable patient information and professional guidance can be found through specialist resources and local sleep clinics (general resources, sleepwalking information, nightmare support, sleep paralysis guidance, hallucination references, sleep-related eating disorder pages).