The exact cause of narcolepsy is not fully understood, but some studies suggest that it could be a genetic disorder (a condition that is passed on from one family member to another).
A number of other factors may contribute to causing narcolepsy. However, before discussing these factors, it is useful to compare what happens during a normal sleep pattern to what happens during a sleep pattern that is affected by narcolepsy.
Normal sleep pattern
When you fall asleep, your body goes through two main stages:
- non-rapid eye movement (NREM) is the first stage
- rapid eye movement (REM) is the second stage
During NREM sleep, your brain activity slows down. You are usually in NREM sleep for one to two hours before entering REM sleep. During REM, your brain activity starts to increase and dreaming can occur.
Narcolepsy sleep pattern
If you have narcolepsy, you do not experience NREM sleep. Instead, your body immediately enters the second stage of sleep (REM). This means that you may start to have vivid dreams almost as soon as you fall asleep. You may also go straight into REM sleep at inappropriate times.
Brain chemicals
Some research has suggested that narcolepsy may be caused by a chemical imbalance in the brain. Chemicals, such as hypocretin, are responsible for regulating your sleep. Hypocretin helps you to wake up after you have been sleeping, then it ensures that you stay awake.
Tests have shown that people with narcolepsy have lower than average levels of hypocretin in their brain, which scientists believe is one of the factors responsible for causing irregular sleep patterns.
It is not known why the brain chemicals become imbalanced in people with narcolepsy. However, one theory is that it may occur as a result of the immune system attacking the cells that produce hypocretin. The immune system usually protects the body from illness and infection, but sometimes it can attack the body's healthy cells and tissues as well.
Other causes
More than half of people with narcolepsy have reported an important event in the days or weeks before the onset of their symptoms. These include:
- pregnancy
- a major psychological stress
- a sudden change of sleep pattern
- a head trauma
