Exploding head syndrome: what it is, causes and what helps

Exploding head syndrome is a sleep experience in which a person hears a sudden loud noise, such as a bang, crash or explosion, as they fall asleep. The Sleep Charity stresses that the sound is not real but can feel very real and may be frightening, and that some people also experience sudden muscle jerks at the same time.

The Sleep Charity places it alongside hypnagogic hallucinations, which happen in the short period between being awake and falling asleep and can involve seeing, hearing or feeling things that are not really there. These are different from nightmares, which happen during sleep. They also describe other experiences that can occur around sleep onset: sleep paralysis, hypnic jerks (sudden muscle twitches or a feeling of jumping), a sensation of falling, and seeing bright flashes of light or hearing loud noises as you drift off.

The Sleep Foundation, a US sleep information site, describes exploding head syndrome as a parasomnia in which episodes typically occur during the transition between sleep and wakefulness, are usually brief, lasting less than a second, and are not associated with physical pain.

People describe a very loud bang or explosion inside the head, sometimes with a flash of light or a jerk of the body, followed by a feeling of fear. The Sleep Foundation says feelings of fright immediately afterwards are common, as are signs of fear such as sweating, palpitations and difficulty breathing, and that people who have more than one episode in a night may lose sleep. It cites a 2020 survey of 3,286 people in which about 44% reported significant fear on waking.

The Sleep Foundation also says some people see flashes of light during episodes, and that the diagnostic criteria require no significant physical pain during or after the episode.

The cause is not known. The Sleep Foundation says the condition has been described since the 1870s but has not been extensively studied, and that in most cases people do not notice any factor leading up to episodes, though some say they have more when stressed or tired.

For hypnagogic hallucinations in general, the Sleep Charity lists alcohol or drug use, stress, anxiety or poor sleep, and narcolepsy (a sleep disorder in which hypnagogic hallucinations and sleep paralysis are common symptoms) as reasons they can occur. NHS guidance for clinicians notes that sleep deprivation is a common precipitant of parasomnias in general, and that intoxication or withdrawal, other sleep disorders and medical or psychiatric causes should be ruled out.

No. The Sleep Charity says it is not dangerous and does not cause pain, and that although these experiences can feel unsettling they are usually harmless. The Sleep Foundation adds that it does not damage the brain or ears, and that primary management includes education and reassurance about its benign nature; some people have fewer episodes after hearing this information.

The Sleep Foundation says to seek medical advice if episodes come with unusual symptoms such as loss of consciousness, seizures, severe headaches or other new neurological symptoms, which are not typical of exploding head syndrome and may point to another condition.

The Sleep Charity says simple lifestyle changes can often reduce symptoms.

• Keep a regular sleep routine.

• Make time to relax and manage stress.

• Get enough sleep each night.

• Avoid alcohol and recreational drugs.

• Seek support for anxiety or other mental health concerns if needed.

The Sleep Charity says it is a good idea to speak to your GP if episodes are happening often, causing worry or distress, or affecting your sleep. Because hypnagogic hallucinations can sometimes be linked to narcolepsy, frequent episodes should be checked by a GP or sleep specialist.

NHS guidance for primary care clinicians (BNSSG) says not all parasomnias need referral: referral is only required if the episodes are frequent, causing harm to the individual or their bed partner, or causing daytime sleepiness. It says parasomnias are usually diagnosed with history, a sleep diary and occasionally polysomnography (a sleep study), and that the general treatment is to ensure good-quality sleep, including good sleep hygiene, treating underlying sleep disorders such as sleep apnoea, insomnia and restless legs, limiting alcohol and recreational drugs, and that drug treatment should not be started in primary care.

The Sleep Foundation says the condition is sometimes distinguished from sudden-onset headache syndromes such as thunderclap headache, which cause pain and commonly occur while awake, and that doctors may consider nocturnal epilepsy, hypnic headaches and post-traumatic stress disorder. Exploding head syndrome involves a noise or flash without pain.

It is also different from sleep paralysis and nightmares, which the Sleep Charity describes separately, though some people have several of these sleep-onset experiences together.

Exploding head syndrome is usually managed in primary care with reassurance and sleep advice. A GP can refer to a sleep clinic if episodes are frequent or disruptive, or another sleep disorder is suspected. Some people choose a private sleep specialist, but because the condition is harmless and there is no standard medicine for it, reassurance, good sleep habits and managing stress are usually the main approach in either setting.