Exploding Head Syndrome: Why You Hear a Bang While Falling Asleep

Have you ever been on the verge of sleep, then suddenly jolted awake as though a bomb had detonated inside your head? If so, you have probably encountered exploding head syndrome, an unusual sleep disorder that remains poorly understood.

Exploding head syndrome (EHS) is part of a group of sleep disorders called parasomnias. Sleep paralysis and hypnic jerks also fall into this category; hypnic jerks are responsible for the unsettling sensation of falling that can occur as we begin to sleep.

Medical professionals have recognised EHS since at least 1876, and the French philosopher and scientist René Descartes is thought to have experienced it. Even so, remarkably little is known about the condition.

Exploding head syndrome symptoms

An EHS episode typically involves an abrupt, loud sound or a feeling of an explosion within the head while moving from wakefulness into sleep. The noises people perceive vary widely, ranging from gunshots and slamming doors to indistinct screaming.

Crucially, these sounds are always brief, lasting only a few seconds or less. They are extremely loud, yet have no apparent source in the surrounding environment.

Some people also experience short visual hallucinations alongside the sounds, including bright flashes of light. Others report intense heat or a feeling that an electrical charge is travelling through the upper body.

How common is exploding head syndrome?

Determining precisely how many people experience EHS is difficult, largely because there is so little available evidence. Just a small number of studies have examined how prevalent EHS is among the general population.

An early study reported that 11 percent of otherwise healthy adults had experienced EHS. Another study of undergraduate students found that 17 percent of participants had experienced repeated episodes during their lives.

In my own more recent research, also involving undergraduate students, my colleagues and I found that one-third of the sample had experienced at least one EHS episode in their lifetime. Around 6 percent reported having at least one episode each month.

Together, these findings suggest that EHS is fairly common, at least among young adults. However, it appears less prevalent than other parasomnias, such as hypnic jerks, which affect up to 70 percent of people.

Triggers

The precise cause of EHS is not known. Although several explanations have been proposed, the leading theory concerns the brain’s natural processes during the shift from wakefulness to sleep. On a normal night, activity in the brain’s reticular formation decreases as we move from being awake into sleep.

Located mainly in the brainstem and hypothalamus, the reticular formation is a collection of brain structures that functions as an "on-off" switch for the brain. As its activity slows during the transition to sleep, the sensory cortices responsible for sight, sound and movement begin to switch off.

It has been suggested that EHS results from an interruption to this usual shut-down process. This may produce a delayed, disconnected burst of neuronal activity in sensory networks without any external stimulus. Those short bursts are then experienced as the loud, indistinct noises associated with EHS.

While the neural basis of EHS is still speculative, we are beginning to understand more about the factors that may make an episode more likely. In one of the first studies to examine associated factors, my colleagues and I found that wellbeing measures, including life stress, were linked with experiencing EHS.

Insomnia symptoms mediated this association. Put differently, life stress was not directly connected with EHS; instead, it had an indirect relationship by first disrupting normal sleeping patterns.

Is EHS dangerous?

Despite its dramatic name, EHS is harmless. However, it is important to tell an EHS episode apart from other conditions, especially different forms of headache.

Episodes of EHS are very brief, usually lasting several seconds, and generally involve no pain. When pain does occur, it is mild and short-lived. By comparison, many headaches persist for longer and involve considerably greater pain.

That does not mean EHS cannot be frightening. In a recent survey of more than 3,000 people who had experienced EHS, 45 percent of respondents said their EHS caused moderate to severe fear.

One-quarter of participants also reported high levels of distress after experiencing EHS. Greater distress was associated with having more frequent episodes.

Unfortunately, no systematic studies have yet examined treatments or coping approaches for people struggling with distressing EHS experiences.

In our survey, participants said that altering their sleeping position to avoid lying on their back, changing their sleep routines and using mindfulness techniques were all helpful ways to prevent EHS. It remains unclear whether these approaches will prove effective in clinical trials.

Reassuringly, simply understanding that EHS is both common and harmless can make a substantial difference. One patient case study reported that reassurance and education about the experience stopped the episodes occurring.

For the time being, the most useful advice appears to be recognising that these experiences are natural and do not mean anything is wrong. Straightforward measures, including better sleep habits, may help to prevent distressing episodes.

Dan Denis, Lecturer in Psychology, University of York

This article is republished from The Conversation under a Creative Commons licence. Read the original article.