What is narcolepsy?

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A rare neurological condition that affects sleeping and waking

Narcolepsy is a rare neurological condition that affects the brain's ability to regulate the normal sleep-wake cycle. It is now generally believed that, in most cases at least, narcolepsy is an auto-immune disorder, caused by the destruction of certain cells within the brain by the body's own immune system. Those cells are responsible for the production of a molecule that plays an important part in regulating the sleep-wake cycle by maintaining stable wakefulness and preventing the onset of sleep during the day. This can lead to symptoms such as disturbed night-time sleep and excessive sleepiness throughout the day. Consequently, narcolepsy is often thought of as a sleep disorder, but its underlying cause means that it is better classified as a disorder of the central nervous system.

How common is it?

Narcolepsy is estimated to affect about 1 person in 2,500. That means that in the UK there are approximately 30,000 people who have narcolepsy. Rare diseases such as this are sometimes referred to as “orphan diseases”.

What happens in normal sleep?

Normal sleep takes the form of a regular pattern of REM (Rapid Eye Movement) and non-REM stages. During a fully night's sleep, every 90 minutes or so a normal sleeper experiences several minutes of REM sleep, during which dreaming occurs, before switching back to non-REM sleep.

And what happens in narcolepsy?

In people with narcolepsy, however, the nocturnal sleep pattern is much more fragmented and typically involves numerous awakenings. When falling asleep at night, or during the day, people with narcolepsy may rapidly enter REM sleep, leading to unusual dream-like phenomena such as hallucinations.

There are several symptoms, but not everyone has all of them

There are four key symptoms of narcolepsy, though people with narcolepsy often exhibit only some:

Excessive daytime sleepiness (EDS)

Falling asleep at inappropriate times throughout the day and/or experiencing chronic pervasive sleepiness and fatigue. Excessive sleepiness will also produce poor concentration and attention with effects on short term memory. At least part of the sleepiness may be secondary to disturbed night-time sleep.


The most specific symptom in narcolepsy but it does not appear in all patients. Around a third of all patients with narcolepsy do not have cataplexy. Cataplexy attacks involve a temporary involuntary muscle weakness in response to emotions or the anticipation of emotion. Positive emotions such as laughter are the most potent triggers, though other emotions such as anger, fear, embarrassment and surprise may also provoke attacks. The severity of a cataplexy attack can vary from mild facial weakness to buckling of the knees and collapse, but without loss of consciousness. Cataplexy attacks can last for seconds or up to two minutes and can occur repeatedly for up to 20-60 minutes.

Sleep paralysis

An inability to move while being conscious either when falling asleep or when waking from sleep. This usually lasts for a couple of minutes, but can last for up to 30 minutes.

Hypnagogic hallucinations

Vivid, frequently frightening dream-like experiences that occur during the transition between sleep and wakefulness. They may accompany sleep paralysis.