What are parasomnias?

Most people think of sleep as a period of complete unconsciousness and physical stillness. In reality the brain cycles through several distinct stages across the night, each with its own patterns of brain activity and muscle tone. Occasionally the transitions between sleeping and waking do not happen cleanly, and behaviours emerge that can look surprising, alarming, or even dangerous.

These are parasomnias: unwanted behaviours or experiences that occur during sleep, or while moving between sleep and wakefulness. They range from the very common — sleep talking, sleepwalking — to more complex activities including sleep eating, sleep-related sexual behaviours, and in rare cases driving while asleep.

Although they can be distressing for the individual and their family, parasomnias are usually benign and, in most cases, highly manageable. They are best understood as disorders of state regulation, where elements of sleep and wakefulness overlap. They do not represent abnormal sleep in itself — they reflect incomplete transitions between different states of consciousness.

Two different types — and why the distinction matters.

Parasomnias divide into two broad groups, and separating them is the single most important step in assessment. They arise from different sleep stages, through different mechanisms, and carry very different clinical implications.

Non-REM parasomnias

During a non-REM episode, the parts of the brain responsible for movement become activated while the regions responsible for conscious awareness remain asleep. The person may sit up in bed, walk around the house, talk incoherently, open doors, or carry out simple automatic behaviours. Most have little or no recollection the following morning.

REM Sleep Behaviour Disorder

Normally during REM sleep the brain temporarily switches off muscle activity, which is what stops us physically acting out our dreams. In REM Sleep Behaviour Disorder (RBD) that paralysis is lost, allowing the individual to move, shout, punch, kick, or enact dreams. Because REM sleep is more abundant later in the night, these episodes tend to occur in the second half.

In some older adults — particularly men over the age of 50 — RBD can occasionally be an early marker of neurological conditions involving abnormal alpha-synuclein protein accumulation, including Parkinson’s disease. This association is clinically important, but it is relatively uncommon and entirely distinct from the familiar childhood sleepwalking seen in non-REM parasomnias.

What is sleepwalking?

Sleepwalking, or somnambulism, is one of the most common non-REM parasomnias. During an episode the individual may appear awake — eyes open, walking around, performing simple tasks, occasionally speaking — but they remain largely asleep and are usually difficult to communicate with. Most remember little or nothing afterwards.

Who gets it?

Sleepwalking is particularly common in childhood. Many children experience occasional episodes, most of which resolve naturally during adolescence. In adults, sleepwalking usually represents the continuation of a lifelong tendency rather than something that develops for the first time.

There is a strong genetic influence. Many people find that one or both parents sleepwalked, that siblings have similar behaviours, or that other family members experienced sleep terrors or sleep talking. This familial pattern points to an inherited tendency towards incomplete arousal from deep sleep.

What makes it worse?

The predisposition may be lifelong, but episodes typically become more frequent when deep sleep is disturbed. Common triggers include sleep deprivation, emotional stress, alcohol, fever, shift work, circadian rhythm disruption, and sleeping somewhere unfamiliar. Each of these increases instability during deep sleep and makes incomplete arousals more likely.

Other non-REM parasomnias

Sleepwalking frequently exists alongside related behaviours, and it is common for one person to experience several across their lifetime.

Is sleepwalking dangerous?

For most people, sleepwalking itself is not harmful. The main concern is accidental injury. Potential risks include falling downstairs, walking outdoors, cooking, handling sharp objects, and driving.

Simple environmental precautions substantially reduce that risk in most cases — and they are usually the first thing we address, before any consideration of investigation or treatment.

How are parasomnias diagnosed?

For many individuals, diagnosis rests primarily on a detailed clinical history. We consider age at onset, family history, the description of events, their timing during the night, frequency, triggers, and any associated sleep disorders.

Descriptions from a partner or family member are often extremely valuable, since the person having the episodes usually cannot describe them. Video recordings captured on a smartphone can also help clarify the picture.

When is further investigation needed?

Sleep studies are not required for everyone. Overnight video polysomnography may be recommended when:

Video polysomnography remains the gold-standard investigation for complex parasomnias, because it captures brain activity, muscle activity, breathing and continuous video simultaneously — which is what allows non-REM parasomnia, RBD and nocturnal epilepsy to be told apart.

How are parasomnias managed?

Most non-REM parasomnias can be managed without medication.

Lifestyle measures

Management focuses on reducing the factors that destabilise deep sleep: maintaining regular sleep schedules, avoiding sleep deprivation, reducing evening alcohol, managing stress, and optimising treatment of any other sleep disorder.

Environmental safety

Equally important, and often the fastest win. Simple measures include locking external doors, installing stair gates where appropriate, removing dangerous objects, and sleeping on the ground floor where injury risk is high.

Behavioural therapy

There is growing interest in Cognitive Behavioural Therapy for Parasomnias (CBT-P). The research is still evolving, but early evidence suggests behavioural approaches may reduce episode frequency by addressing stress, sleep stability, conditioned arousal, and the anxiety that builds up around the episodes themselves.

Medical treatment

Medication is rarely required. In severe or high-risk cases, specialist sleep physicians may consider carefully selected pharmacological treatment, but only after excluding underlying sleep disorders and addressing behavioural factors first. Treatment is always individualised and generally reserved for episodes that remain frequent, disruptive, or pose a significant safety risk.

The Grace Sleep approach

Parasomnias are often unsettling for individuals and their families. Our first priority is to establish whether the behaviour represents a benign non-REM parasomnia or a less common condition requiring further investigation.

Our assessment considers detailed clinical history, family history, sleep patterns, lifestyle and stress, circadian rhythm, potential triggering sleep disorders, and home video polysomnography where appropriate.

For most patients, reassurance, education and practical management strategies are all that is required. For those with more complex symptoms, our multidisciplinary team provides access to advanced diagnostics and personalised treatment pathways. The aim is to improve both safety and sleep quality, while helping families feel confident about what is happening overnight.

Frequently asked questions