Parasomnias can be confusing for the person experiencing them and for the people around them. Learning how sleep and wakefulness can overlap may make these experiences easier to understand. This section explains what parasomnias are, how REM- and NREM-related experiences can differ, what may contribute to them, and some common misconceptions. 

This information is educational. It cannot determine whether you or someone you know has a particular sleep disorder. 

What Are Parasomnias?

Parasomnias are unusual behaviours or experiences that occur during sleep, while falling asleep, or while waking. Depending on the condition, an episode may involve movement, speech, confusion, fear, vivid dream experiences, or temporary difficulty moving. 

Parasomnia is an umbrella term, not a single condition. Different parasomnias can look similar from the outside, even though they may arise from different stages of sleep or involve different levels of awareness and memory. 

Examples discussed on this website include: 

• Sleepwalking 

• Sleep talking 

• Sleep terrors 

• Nightmare disorder 

• Sleep paralysis 

• REM sleep behaviour disorder 

• Confusional arousals 

• Sleep-related bruxism 

During some episodes, parts of the brain appear to remain in a sleep-like state while other parts support behaviour or awareness. This can help explain why someone may sit up, speak, walk, or appear frightened without being fully awake. 

The person is not performing these behaviours intentionally. They may have little or no memory of the event afterward, depending on the type of episode. 

An unusual event during the night is not automatically a parasomnia. Some nighttime symptoms can overlap with other sleep, neurological, medical, medication-related, or mental-health concerns. A healthcare professional may need to consider the complete pattern before identifying the most likely explanation. 

Based primarily on: Irfan et al. (2021); Stefani and Högl (2021); Dauvilliers et al. (2018); Roguski et al. (2020). 

Understanding REM and NREM sleep 

Sleep is not one continuous, unchanging state. The brain moves through different stages throughout the night, including rapid eye movement—or REM—sleep and non-rapid eye movement—or NREM—sleep. 

Different sleep-related experiences are associated with different stages or transitions. However, the timing or appearance of an episode cannot establish a diagnosis on its own. 

NREM-related parasomnias 

Sleepwalking, sleep terrors, and confusional arousals are described as NREM disorders of arousal. They involve an incomplete transition from deeper NREM sleep toward wakefulness. 

During an episode, a person may: 

• Appear awake without being fully aware 

• Have their eyes open 

• Speak or make sounds 

• Respond slowly or inappropriately 

• Appear confused or frightened 

• Sit up, walk, or perform other behaviours 

• Have limited or no memory of the event the following day 

NREM episodes commonly arise from deep sleep. They may be influenced by factors that increase the pressure for deep sleep or repeatedly interrupt sleep. 

Although these conditions share certain features, they are not identical: 

• Confusional arousals mainly involve confusion or disorientation during an incomplete awakening. The person may remain in bed. 

• Sleepwalking involves getting out of bed or performing other behaviours while awareness remains impaired. 

• Sleep terrors involve a sudden display of intense fear, such as screaming or crying, together with strong physical signs of activation. 

REM-related parasomnias 

REM sleep is strongly associated with vivid dreaming. Nightmare disorder, sleep paralysis, and REM sleep behaviour disorder are discussed in the supplied articles as REM-related conditions or experiences. 

They affect REM sleep in different ways: 

• Nightmare disorder involves repeated, distressing, well-remembered dreams. The person generally becomes alert after awakening and can recall the dream. 

• Sleep paralysis occurs when the temporary muscle immobility associated with REM sleep continues briefly as a person becomes aware while falling asleep or waking. 

• REM sleep behaviour disorder involves movements or vocalizations associated with dreams because the usual reduction in muscle activity during REM sleep is impaired. 

REM-related conditions should not be treated as interchangeable. For example, being unable to move during sleep paralysis is different from moving forcefully during REM sleep behaviour disorder. 

Where do sleep talking and bruxism fit? 

Sleep talking can occur during different stages of sleep. It may occur on its own or alongside another sleep-related event. The person is often unaware of what they said and may not remember speaking. 

Sleep-related bruxism involves repetitive jaw-muscle activity during sleep, including grinding, clenching, or jaw bracing. It differs from experiences such as sleepwalking or nightmares because it primarily involves jaw-muscle activity. It is included on this website because it is an important sleep-related behaviour that may affect patients and families. 

Based primarily on: Irfan et al. (2021); Stefani and Högl (2021); Sharpless (2016); Dauvilliers et al. (2018); Cleveland Clinic (2021, sleep talking); Guaita and Högl (2016). 

Why do parasomnias happen? 

There is not one cause that explains every parasomnia. Different conditions may involve different sleep processes, and more than one factor may contribute to an individual’s episodes. 

Some factors may increase the likelihood of an episode without being its sole cause. 

Incomplete transitions between sleep and wakefulness 

The NREM disorders of arousal reviewed by Irfan and colleagues involve an incomplete transition from deep sleep toward wakefulness. A person may be able to move or speak while awareness, judgment, and memory remain partly sleep-like. 

This mixture of sleep and wakefulness can help explain why the person’s behaviour may appear purposeful even though they are not fully conscious of what they are doing. 

Sleep loss 

Sleep deprivation can increase the pressure for deeper sleep and may make NREM disorders of arousal more likely in susceptible people. 

Insufficient sleep is also identified as a predisposing factor for isolated sleep paralysis. Protecting adequate sleep may therefore be relevant across several conditions, although it is not a guaranteed way to prevent every episode. 

Irregular sleep schedules 

Changes in sleep timing, circadian disruption, and jet lag are identified as possible contributors to sleep paralysis. Irregular schedules may also affect the stability and quality of sleep more broadly. 

Interrupted or fragmented sleep 

Noise, pain, breathing-related sleep disruption, movement-related sleep disruption, and other repeated disturbances may contribute to partial awakenings. 

For NREM disorders of arousal, the supplied review describes episodes as potentially occurring when deep sleep is repeatedly disrupted while the drive to remain asleep is still strong. 

Stress and emotional factors 

Stress, anxiety, trauma, and other emotional factors may affect sleep and may be relevant to some conditions. Their role is not identical across all parasomnias. 

Nightmare disorder, particularly when associated with trauma or psychiatric conditions, may involve heightened arousal, disturbed emotional processing, and difficulty reducing learned fear responses. 

Stress sensitivity is also commonly reported by people with bruxism, although the bruxism treatment review notes that evidence for many behavioural interventions remains limited. 

Experiencing a parasomnia does not automatically mean that a person has an underlying psychological disorder. 

Medications and substances 

Some medications and substances may trigger, worsen, or change sleep-related experiences in certain people. The relationship depends on the medication, the condition, and the individual. 

A healthcare professional may ask about: 

• Prescription medications 

• Non-prescription medications 

• Supplements 

• Alcohol or other substances 

• Recent changes in dose or timing 

Do not stop or change a prescribed medication without first speaking with a physician or pharmacist. 

Other sleep or health conditions 

A parasomnia may occur alongside another sleep condition. In some situations, identifying and treating a contributing condition may reduce episodes. 

The supplied articles discuss possible overlap with conditions that interrupt sleep, affect REM sleep, or increase sleep instability. This is one reason professional assessment may be important when events are frequent, new, dangerous, or difficult to identify. 

Individual and family susceptibility 

Some NREM parasomnias occur more often within families, suggesting that inherited susceptibility may play a role. However, having a family member with a parasomnia does not mean that another family member will necessarily develop one. 

Age and development 

Some NREM parasomnias are particularly common during childhood. They may decrease as a child grows, but they can persist or occur in adults. 

New or concerning events in adulthood should not automatically be assumed to be the same as common childhood episodes. The person’s complete history, symptoms, safety risks, and possible contributing factors should be considered. 

Based primarily on: Irfan et al. (2021); Stefani and Högl (2021); Sharpless (2016); Guaita and Högl (2016); Dauvilliers et al. (2018). 

Common Myths & Misconceptions

“People experiencing a parasomnia are awake.” 

A person may have their eyes open, speak, walk, or perform other behaviours without being fully awake. Awareness and responsiveness differ between conditions. 

“They are doing it on purpose.” 

Parasomnia behaviours occur during sleep or an incomplete transition between sleep and wakefulness. They are not intentional actions. 

“Everyone remembers what happened.” 

Memory varies. People with sleepwalking, sleep terrors, or confusional arousals may have little or no memory afterward. People awakening from a nightmare often remember the dream. People with REM sleep behaviour disorder may also remember dream content associated with their movements. 

“A night terror is just a very bad nightmare.” 

Night terrors and nightmares have different typical patterns. A person awakening from a nightmare is generally alert and can describe the dream. During a sleep terror, the person may appear intensely frightened but remain difficult to awaken or comfort and may remember little afterward. 

“You should always wake someone during an episode.” 

The appropriate response depends on the situation. Abrupt attempts to wake or restrain someone experiencing a NREM episode may increase confusion or agitation. 

Immediate safety should come first. If there is no immediate danger, remaining calm and gently guiding the person away from hazards may be more appropriate. Detailed guidance is available in the “What Can I Do?” section. 

“You should never wake a sleepwalker.” 

This statement is also too absolute. A person may need to be awakened if they cannot otherwise be moved away from immediate danger. If waking is necessary, it should be done as calmly and gently as possible. 

“Sleep talking reveals someone’s true thoughts or secrets.” 

Speech during sleep may be unclear, fragmented, or unrelated to waking beliefs and intentions. It should not be treated as a reliable or intentional statement. 

“Sleep paralysis means something dangerous is physically holding the person down.” 

During sleep paralysis, awareness returns while REM-related muscle immobility briefly continues. The experience can include vivid sensations or perceptions and can feel frightening, but the experience is related to the sleep–wake transition. 

Repeated or highly distressing episodes can still be discussed with a healthcare professional. 

“Moving during a dream is always normal.” 

Small movements can occur during sleep, but repeated forceful dream-enacting behaviour—such as punching, kicking, or falling from bed—may create a risk of injury and should be medically assessed. 

“Teeth grinding is harmless.” 

Sleep-related bruxism does not affect everyone in the same way. It may be associated with grinding sounds, tooth wear, jaw discomfort, muscle fatigue, or headaches. 

A dental or healthcare assessment can help determine whether protection or treatment is appropriate. 

“Every parasomnia needs medication.” 

Some episodes may not require medication. Depending on the condition, care may focus on education, reassurance, adequate sleep, addressing contributing conditions, psychological or behavioural treatment, dental protection, environmental safety, or condition-specific medication. 

The evidence for treatment differs considerably between conditions. 

“One medication can treat every parasomnia.” 

There is no single medication for all parasomnias. Treatments studied for one condition may be ineffective, inappropriate, or potentially harmful for another. 

Medication should only be considered with a qualified professional who has reviewed the person’s symptoms, health history, other medications, and possible diagnosis. 

“Parasomnias only affect children.” 

Some NREM disorders of arousal are particularly common in childhood, but parasomnias can also persist into adulthood or begin later in life. 

“An online description can tell me which condition I have.” 

Online information may help someone recognize patterns and prepare questions. Diagnosis may require a detailed history, information from a witness, medication and health review, examination, or—in selected cases—a sleep study. 

Based primarily on: Irfan et al. (2021); Stefani and Högl (2021); Sharpless (2016); Dauvilliers et al. (2018); Roguski et al. (2020); Cleveland Clinic (2021, sleep talking); Guaita and Högl (2016). 

When should I learn more or seek advice? 

Consider speaking with a healthcare professional when an episode: 

• Causes an injury or creates a risk of injury 

• Involves leaving the home or another dangerous activity 

• Includes repeated punching, kicking, or falling from bed 

• Is frequent, worsening, or highly distressing 

• Begins unexpectedly in adulthood 

• Seriously disrupts sleep 

• Affects mood, concentration, school, work, or relationships 

• Occurs alongside other concerning sleep or health symptoms 

• May be connected to a medication or substance 

Seek urgent assistance when there is an immediate threat to safety, a serious injury, or another medical emergency. 

Learning about parasomnias is a useful first step, but you do not need to identify the condition by yourself. A healthcare professional can help review the complete pattern and discuss appropriate next steps.