Australasian Science: Australia's authority on science since 1938

Things that Go Bang in the Night

By Tim Hannan

Exploding head syndrome, which results from neurological dysfunction during the sleep–wake transition, may be more widespread than realised.

In recent years, the neuropsychological literature has been awash with reports of people describing strange experiences when going to sleep. Many of these have described hearing sudden inexplicable noises, such as unseen bombs exploding nearby, thunderclaps on cloud-free nights, or a gun fired in their bedroom by an invisible intruder. At times these sounds are accompanied by flashes of light, or by physical sensations such as intense heat.

While some people are convinced that these explosions are real, most others acknowledge that, since they are not heard by others, the sounds must have occurred inside their own heads. Some have concluded that these noises must be the work of invisible agents such as aliens or poltergeists, or a government agency testing mind-control weapons; for others they are taken as signs of the emergence of a serious mental or neurological disorder.

However, neurological investigations suggest that the episodes are symptoms of a condition labelled exploding head syndrome, which may be much more common than previously assumed.

The earliest known description of exploding head syndrome in the scientific literature is from 1876, when an American physician reported a patient’s description of:

a sense of a pistol shot or a blow on the head ... a noise in my head, which is sometimes like the sound of a bell, which has been struck once … or else I hear a loud noise, which is most like that of a guitar string, rudely struck, and which breaks with a twang.

A later report by a Welsh psychiatrist employed the term “snapping of the brain” to describe his patients’ symptoms. The condition’s current nomenclature derives from a British neurologist’s comprehensive review of the symptoms of 54 patients in the 1980s.

The neurological mechanisms responsible for exploding head syndrome are not well understood. The dominant theory implicates the reticular formation, a set of connected nuclei distributed through the brainstem, which is one of several neural systems regulating the body’s transitions between sleep and wakefulness. It is believed that this network serves to switch off bodily functions in stages as sleep commences, with sensory-motor reflexes, eye movements and motor control progressively inhibited.

This process is disrupted in those with exploding head syndrome, with the region producing a rapid flurry of neural firing that activates the neurons of the auditory processing system and certain other regions, giving rise to the perception of loud noises that are sometimes accompanied by flashes of light, physical sensations and movements.

Dysfunction in the reticular formation has also been implicated in episodes of sleep paralysis, in which a person is unable to move or speak immediately upon waking.

Previously thought to be rare and predominantly occurring in older adults, a recent study has suggested that exploding head syndrome may be markedly under-recognised. In a paper in the current issue of the Journal of Sleep Research, Brian Sharpless of Washington State University noted that 18% of more than 200 college students reported experiencing this at least once, and most of these reported recurrent episodes. One-third of these sufferers also experienced one or more episodes of sleep paralysis, reinforcing the assumption that these conditions are intrinsically related.

Case reports suggest that exploding head syndrome may be intermittent, and are more likely to occur during periods of heightened stress or fatigue. Its benign nature is reflected in its lack of correlation with or prediction of any other health condition. Indeed, few participants in the Washington State University study reported that it interfered with their daily lives, although other reports suggest that a proportion of sufferers struggle with the effects of disrupted sleep on daytime functioning.

At present there is no empirically supported treatment for exploding head syndrome. Interventions are mainly directed at education to reduce fears of neurological or psychiatric illness.

The recent increase in reports of exploding head syndrome is unlikely to reflect a true change in incidence, but rather improved recognition due to increasing awareness of sleep-related disorders among the public and health professionals.

Those who experience such symptoms can be reassured that unexplained sounds do not reflect the covert actions of a malevolent government. Of course, that’s just what they would want you to believe.

A/Prof Tim Hannan is Head of the School of Psychology at Charles Sturt University, and the Past President of the Australian Psychological Society.