What is Parasomnia? Causes, Types, Symptoms and Treatment (UK Guide)

For most people, sleep is a refuge — a time to rest, reset, and recover. But for those living with parasomnia, sleep becomes something far more unpredictable. It may involve waking up in strange places, shouting without reason, or acting out dreams as though they were real. The line between sleep and wakefulness blurs. And often, the person affected has no memory of what happened.

Parasomnia is not one condition, but a category of sleep disorders involving abnormal behaviours, movements, or experiences during sleep. Some of them sound benign — talking in your sleep, for example — while others, like sleepwalking or REM sleep behaviour disorder, can be risky or even dangerous. In the UK, parasomnia is more common than most realise, particularly among children, but also affects a significant number of adults.

This guide explores what parasomnia is, the different ways it presents, what causes it, how it’s diagnosed in the UK, and what kinds of treatment actually help.

Parasomnia refers to unusual or disruptive behaviours that occur while falling asleep, during sleep, or in the moments between sleep and wakefulness. These episodes can last anywhere from a few seconds to several minutes. What unites them is that they emerge from partial arousals — the brain is neither fully asleep nor fully awake.

The NHS states: "A parasomnia is an experience or behaviour that occurs when you are asleep". These can involve movements, emotions, perceptions, dreams, or autonomic nervous system activity (like rapid heart rate or sweating). Most people experiencing parasomnias have no memory of the episode the next morning.

What makes parasomnias particularly tricky is that they don’t always respond to standard sleep advice. Someone may follow all the right rules — no caffeine, a consistent bedtime, no screens — and still find themselves sitting bolt upright at 2am, panicked and confused, or halfway down the stairs in the dark.

How Parasomnias Show Up

Parasomnias fall into several recognised categories based on the sleep phase in which they occur. Each has its own distinctive features.

Some parasomnias occur during non-rapid eye movement (NREM) sleep — especially the deep stages of sleep early in the night. These include things like sleepwalking, sleep terrors, and confusional arousals. During these episodes, the person is caught in a state between sleep and wakefulness. They may appear awake — eyes open, talking, even walking — but they’re not fully conscious and are often unresponsive.

Other parasomnias arise from REM (rapid eye movement) sleep, which is when most vivid dreaming occurs. These include REM sleep behaviour disorder, in which someone physically acts out their dreams, and sleep paralysis, where the body is temporarily frozen on waking or falling asleep, often with terrifying hallucinations.

Still others don’t fall neatly into either category, like sleep-related eating disorder or sexsomnia — both of which are real and well-documented, albeit poorly understood.

What they all share is a disruption of normal sleep architecture, and a capacity to impact both sleep quality and daily functioning.

Causes: Why Parasomnia Happens

No single cause explains all parasomnias. In children, these conditions are often considered part of normal development — the brain hasn’t yet learned how to smoothly transition through sleep stages. Most kids who sleepwalk or have night terrors outgrow them by adolescence.

In adults, parasomnias often point to other underlying issues. Sleep deprivation is a major trigger — the deeper and more abruptly you fall into sleep, the more likely these episodes are. Stress and trauma can also play a role, particularly with nightmares and REM-related disturbances. Certain medications, including antidepressants and antipsychotics, have been linked to parasomnias, as have substances like alcohol and recreational drugs.

Sometimes, parasomnia is associated with neurological conditions. REM sleep behaviour disorder, for instance, has been linked in research to an increased risk of Parkinson’s disease and Lewy body dementia. Not everyone with the disorder will go on to develop a neurodegenerative disease, but the link is well established.

Genetics matter too. If one or both parents had parasomnias, there’s a greater chance their children will as well. And conditions like sleep apnoea can make parasomnias more likely by fragmenting sleep and causing frequent arousal.

Living With Parasomnia

For those affected, parasomnia can be more than just a sleep issue — it can be a source of shame, danger, and disruption. Sleepwalking, for example, isn’t just quirky; it can lead to serious injury. People have walked out of their homes, into traffic, or fallen down stairs. REM sleep behaviour disorder can result in violence, both toward oneself and others.

Then there’s the emotional toll. Imagine waking up with crumbs in the bed, the fridge raided, but no memory of having eaten. Or being told you’ve shouted in your sleep, again, disturbing your partner. Over time, this erodes confidence and can lead to anxiety around bedtime.

Many people with parasomnia delay seeking help because they think it’s rare or untreatable. But neither is true. The NHS recognises parasomnia and offers referral pathways to specialist sleep clinics, where assessments like overnight sleep studies can shed light on what’s happening.

Diagnosis in the UK

In the UK, diagnosis typically begins with a GP. If parasomnia is suspected — based on sleep behaviours, patterns, and safety concerns — the GP may refer to a sleep specialist or neurologist. This often leads to an overnight sleep study, known as polysomnography.

Polysomnography records brain waves, breathing, heart rate, oxygen levels, and body movements during sleep. In some cases, video monitoring is used to catch behaviours in real time. This is especially useful for conditions like REM sleep behaviour disorder, which may not happen every night.

Some patients are asked to keep a sleep diary, documenting when they go to bed, wake up, and experience any strange behaviours. Partners often provide key information too — it’s not unusual for the sleeper to be completely unaware of what’s happening.

Treatment: What Actually Helps

The good news is that parasomnia is often manageable — even if there’s no instant fix. Treatment depends on the type and severity of the parasomnia, as well as what’s causing or triggering it.

For children, reassurance and safety measures are often enough. Most outgrow sleepwalking and night terrors without intervention. It helps to ensure a consistent sleep routine and avoid overstimulation or overtiredness before bed.

In adults, addressing underlying triggers is crucial. If someone is stressed, sleep-deprived, or taking medication known to disrupt sleep, that’s where treatment starts. Improving sleep hygiene — regular wake times, no alcohol before bed, screen-free wind-down routines — can reduce frequency.

Where episodes are frequent, dangerous, or distressing, a referral to a specialist may lead to more tailored interventions. These could include:

• Cognitive behavioural therapy, particularly for anxiety-linked parasomnias

• Techniques for nightmare rescripting or lucid dreaming (especially in PTSD-related cases)

• Treating coexisting conditions like sleep apnoea or restless legs syndrome

Medication is rarely the first step — and when it’s used, it’s with caution. Melatonin is sometimes prescribed off-label for REM sleep behaviour disorder or delayed sleep phase conditions. Other sedatives or antidepressants may be used in certain cases, but always under specialist supervision.

Above all, the priority is keeping the person safe. That might mean locking doors and windows, using bed alarms, padding sharp corners, or even moving to a ground-floor bedroom. What works depends on the type of parasomnia and the level of risk.

When to Get Help

If parasomnia is frequent, escalating, or causing injury — physical or emotional — it’s time to speak to a GP. Similarly, if it’s beginning in adulthood with no clear reason, that warrants a closer look. Some parasomnias are benign. Others are early indicators of broader neurological issues. Getting assessed can make all the difference.

Sleep doesn’t have to be a battleground. With the right support, even the most disruptive parasomnias can be managed. And for many, a good night’s sleep is entirely within reach.