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Causes of Narcolepsy
The exact cause of narcolepsy remains unclear. In normal sleep, the brain’s electrical activity slows down in the first hour of sleep (slow wave sleep).
After a time the electrical activity again increases and is accompanied by rapid eye movements (REM sleep) and deep relaxation of your muscles. If you are woken at this stage you are likely to describe a dream.
This cycle repeats itself a few times a night with decreasing amounts of slow wave sleep and increasing amounts of REM sleep.
When investigating the cause of narcolepsy, it was found that if you have narcolepsy you enter REM sleep more quickly than usual when you fall asleep, sometimes straight away. The sleep cycle is controlled by a complex system of neurones (messenger cells) in the brain stem, thalamus, hypothalamus, and basal forebrain. The neurotransmitter, (a chemical released by one neuron to excite a neighbouring one) hypocretin is produced in the hypothalamus, which is believed to stabilise the activity of other neurone groups involved in the control of sleep and waking.
Research has identified that there is reduced hypocretin in the brains of those who have narcolepsy. Reduced hypocretin helps explain both the rapid transitions between wakefulness and REM sleep and the tendency for these states to break up in narcolepsy.
Symptoms of sleep paralysis and hallucinations immediately before falling asleep are caused by an interference with REM sleep (dreams and deep relaxation of muscles).
It has also been discovered that many people with narcolepsy have a certain tissue type (HLA DR2), which suggests that an autoimmune reaction may be involved, whereby the body attacks itself.
