Other symptoms of narcolepsy may include hallucinations, automatic behaviour during sleep attacks, episodes of muscular weakness or paralysis during waking hours, and an abnormal tendency to pass directly into REM sleep from wakefulness. Despite its relatively high profile, narcolepsy is actually quite rare, affecting about 1 in 2,000 people. However, it is estimated that fewer than half of narcolepsy sufferers are actually correctly diagnosed, and it may often be misinterpreted as a psychological disorder.
The order and length of non-REM and REM sleep become disturbed in narcoleptics, and they typically move into REM sleep very quickly after falling asleep (e.g. within five minutes, rather than the usual hour or more). People with narcolepsy may therefore dream even when they fall asleep for very short periods, and they often remember their dreams in great detail. Dreams may also persist during complete wakefulness, as the dreams of REM sleep “spill over” into the waking state. In fact, narcolepsy is sometimes thought of as a disorder of REM sleep itself, in which wakefulness and REM sleep become mixed up and confused.
Narcoleptics may exhibit “automatic behaviour” during daytime sleep episodes, in which they continue to perform normal daily activities or tasks even though technically asleep, with little or no subsequent recollection of the events or of having slept at all. Hypnagogic hallucinations (vivid, often frightening, dream-like experiences that occur while dozing or falling asleep) or hypnopompic hallucinations (similar experiences on waking), and sleep paralysis (the complete inability to move or speak during the times of falling asleep or waking up) are also common symptoms.
Perhaps the most startling symptom of narcolepsy, though, is cataplexy, a sudden muscular weakness during wakefulness similar to the muscle atonia normally experienced during REM sleep. This is often brought on by strong emotion - laughter, anger, surprise, sexual arousal, etc - and it can range from a slight slackening of the facial muscles to slurred speech and impaired vision to head-dropping and weakness at the knees to total collapse or even complete paralysis. Cataplectic attacks may last from a few seconds to two or three minutes. Even during a period of total collapse, the narcoleptic is still fully awake and can still hear sounds around them - they may even be able to see, if their eyes happen to be open - but they are unable to speak, sit up or make voluntary movements of any sort while the atonia persists. The fact that atonia episodes in narcoleptics are triggered by strong emotions suggest an intriguing connection between emotional behaviour and REM sleep and the disorder, which is still being explored.
Narcolepsy is a neurological and auto-immune disorder, not caused by mental illness or psychological problems, and is probably caused by genetic mutations or abnormalities in the brain, which may in turn be triggered by an environmental event in the brain’s development (e.g. a virus). In recent years, it has been found that a major immediate cause of narcolepsy is the destruction of orexin-producing cells in the brain (orexin, also known as hypocretin, is a neurotransmitter that regulates arousal, wakefulness and appetite). It is thought that the low number of orexin-producing neurons in the brains of narcoleptics is due to gliosis, an inflammatory process associated with neuronal degeneration, possibly due to auto-immune attacks on the neurons or certain sensitivities to environmental toxins.
There is no definitive cure for narcolepsy. Treatment may involve pharmacological stimulants of the central nervous system or antidepressants, although such treatments mainly address the symptoms not the causes. Lifestyle changes like reducing stress, increasing exercise and avoiding caffeine and nicotine may help to some extent, and scheduling short 15-minute naps may help sufferers stay more alert during the day.