A parasomnia is a sleep disorder involving abnormal movements, behaviors, or experiences that happen during sleep or during the transition between waking and sleeping. These can range from mumbling a few words to walking through the house, acting out dreams, or screaming in terror, all without conscious awareness. Parasomnias are surprisingly common: lifetime prevalence rates range from about 4% to 67% depending on the type, and they affect children more often than adults.
How Parasomnias Are Classified
Sleep happens in cycles that alternate between two major phases: NREM (non-rapid eye movement) sleep and REM (rapid eye movement) sleep. Parasomnias are grouped based on which phase they emerge from, because the underlying biology and the types of behaviors differ significantly between the two.
NREM parasomnias tend to arise from deep sleep, typically stage three, and involve a partial awakening where parts of the brain “turn on” while others stay asleep. REM parasomnias happen during the dreaming phase of sleep and involve a breakdown of the normal muscle paralysis that keeps your body still while you dream. A third category covers everything that doesn’t fit neatly into either group, including exploding head syndrome, sleep-related hallucinations, and bedwetting.
NREM Parasomnias: Sleepwalking, Sleep Terrors, and More
The most recognized NREM parasomnias are called “disorders of arousal” because they all share the same core problem: an incomplete transition between deep sleep and wakefulness. Brain imaging during sleepwalking episodes reveals something striking. The motor areas of the brain show wake-like electrical activity, meaning the body can move and perform actions, while the frontal areas responsible for judgment, self-awareness, and memory remain in a deep-sleep pattern. This split explains why people can do complex things during an episode, like rearrange furniture or even drive, yet have no memory of it afterward.
Confusional arousals are the mildest form. A person may sit up in bed, look around with a glazed expression, and appear disoriented for several minutes before settling back to sleep. If they get out of bed, it can progress into sleepwalking.
Sleepwalking ranges from simple wandering around the bedroom to surprisingly complex behaviors like changing lightbulbs, moving furniture, or preparing food. Lifetime prevalence is about 22%, though only around 2% of adults sleepwalk in any given year. The rate is higher in children, at about 5% compared to 1.5% in adults.
Sleep terrors (also called night terrors) involve sudden episodes of intense fear, often with screaming, lashing out, and a racing heart. They commonly overlap with sleepwalking. Despite appearing terrified, the person is not fully awake and usually has little or no memory of the event. About 10% of people experience sleep terrors at some point in their lives.
Sleep-related eating disorder involves episodes of eating during partial arousals from deep sleep, sometimes consuming unusual food combinations or even inedible items, with little or no recall the next morning.
REM Parasomnias: Acting Out Dreams
During normal REM sleep, your brain is highly active but your voluntary muscles are essentially paralyzed. This protective mechanism keeps you from physically acting out your dreams. When that paralysis fails, the result is REM sleep behavior disorder (RBD). People with RBD may punch, kick, shout, or leap out of bed while dreaming, sometimes injuring themselves or a bed partner. About 5% of the general population reports dream enactment behaviors.
RBD carries a unique long-term significance. Research has revealed a strong link between RBD and neurodegenerative diseases, particularly Parkinson’s disease, dementia with Lewy bodies, and a condition called multiple system atrophy. In some cases, RBD precedes the onset of these diseases by decades. As many as half of people with RBD will eventually develop a neurodegenerative condition, making it one of the strongest early warning signs currently known. This is why getting a proper evaluation matters, even if the episodes seem manageable.
Sleep paralysis is essentially the opposite problem: the muscle paralysis of REM sleep persists briefly after waking up (or starts before falling asleep), leaving you temporarily unable to move or speak. It often comes with vivid hallucinations and a feeling of pressure on the chest. It can be terrifying in the moment but is not physically dangerous.
Nightmare disorder involves frequent, intensely disturbing dreams that cause significant distress or impair daytime functioning. Nightmares are the most common parasomnia overall, with a lifetime prevalence of about 66% and a current prevalence of roughly 19%.
Less Common Types
Exploding head syndrome is a benign but alarming condition where you perceive a loud sound, like a gunshot or explosion, in your head during the transition into or out of sleep. It causes no pain, but the sudden jolt and accompanying fear can be deeply unsettling. One study found that up to 16% of college students had experienced at least one episode, and roughly 37% of people with a history of sleep paralysis also reported exploding head syndrome symptoms.
Sleep-related hallucinations, sleep-related groaning (called catathrenia), and bedwetting (sleep enuresis) round out the “other” category. Sleep talking is technically not classified as a parasomnia under current diagnostic standards, though it frequently co-occurs with other parasomnias and has a remarkably high lifetime prevalence of nearly 67%.
What Causes Parasomnias
Parasomnias result from a fundamental problem with the boundaries between sleep states and wakefulness. Instead of cleanly transitioning from one state to another, the brain gets caught in a hybrid condition where features of sleep and wakefulness overlap. What triggers this boundary breakdown varies.
Sleep deprivation is one of the most reliable triggers for NREM parasomnias, because it increases the pressure for deep sleep, making abnormal arousals more likely. Stress, fever, alcohol, and irregular sleep schedules can all provoke episodes in people who are susceptible. There is a genetic component as well: parasomnias, especially sleepwalking and sleep terrors, tend to run in families.
Certain medications can also trigger parasomnias. Sleeping pills like zolpidem and zopiclone are among the most commonly reported causes of drug-induced sleepwalking, because they enhance the activity of a brain chemical involved in deep sleep. Some antipsychotic medications have also been linked to sleepwalking. For REM-related parasomnias, medications that suppress certain neurotransmitters involved in the sleep-wake cycle can promote REM sleep in ways that lead to nightmares or dream enactment. Antidepressants are a well-known example.
How Parasomnias Are Diagnosed
For most people, a diagnosis starts with a detailed clinical interview. Your doctor will ask about the timing, frequency, and nature of episodes, what you remember (if anything), and whether anyone has witnessed the behaviors. Home video recordings captured by a bed partner or family member can be extremely useful, since most people with parasomnias have no awareness of what they do during an episode.
A sleep study, called polysomnography, is sometimes needed to confirm the diagnosis or rule out other conditions. This is especially important for suspected REM sleep behavior disorder, where the study can detect the absence of normal muscle paralysis during REM sleep. It also helps distinguish parasomnias from nocturnal seizures, which can look similar from the outside but require completely different treatment. For NREM parasomnias, the diagnosis is often made clinically without a sleep study, though one may be recommended in ambiguous or severe cases.
Treatment and Management
Treatment depends on the type and severity of the parasomnia. For many NREM parasomnias in children, no specific treatment is needed beyond reassurance and time, as most children outgrow them. In adults, addressing triggers like sleep deprivation, stress, or alcohol use can significantly reduce the frequency of episodes.
For REM sleep behavior disorder, the American Academy of Sleep Medicine recommends that clinicians consider melatonin or a sedative medication, with the choice depending on whether the RBD is isolated, related to another condition, or caused by a medication. When a drug is the suspected trigger, adjusting or stopping that medication may resolve the problem.
Making the Bedroom Safer
Regardless of treatment, creating a safe sleep environment is a priority for anyone with a parasomnia that involves movement. Practical steps include lowering the mattress to the floor if falls are a risk, removing sharp-edged furniture or padding the corners, keeping the bedroom floor clear of clutter, and locking windows and doors. All weapons should be removed from the bedroom, along with heavy or fragile objects that could cause injury if thrown or knocked over.
For people with significant nighttime movements, sleeping in a separate room from a partner may be necessary until the condition is under control. If the home has stairs, safety gates can prevent dangerous falls. Alarms on bedroom doors and exterior windows provide an alert system if someone begins to wander. Sleeping on the ground floor, when possible, further reduces the risk of injury from stairway falls or attempts to leave the home.