Causes of Narcolepsy
Causes of narcolepsy are believed to be from a genetic predisposition and abnormal neurotransmitter (hypocretin, also known as orexin) functioning and sensitivity.
Narcolepsy is a neurological condition associated with a fault in the mechanisms in the brain, which control wakefulness and sleep.
One of the main causes of narcolepsy is the intrusion of rapid eye movement (REM) sleep at inappropriate times. During REM sleep the brain is very active and the muscles of the body relaxed (paralysed).
In non-narcoleptic people REM sleep does not occur until sleep has been underway for some time. However, in people with narcolepsy REM sleep often occurs soon as they fall asleep on even as they are awake.
Causes of narcolepsy may be associated with damage to the amygdala. A cerebral protein has recently been discovered that is decreased in a large number or all narcolepsy patients. The protein involved is called hypocretinor orexin.
Hypocretin: Hypocretin (also called orexin) is a peptide that modulates activity in the hypothalamus (the region in the brain associated with sleep, well being, and appetite).
Hypocretin specifically has properties that promote wakefulness and inhibits REM sleep. They may also have other actions that affect feeding behavior and increase activity in the autonomic (sympathetic) nervous system and systems that regulate motor control.
Another one of the causes of narcolepsy is deficiencies in peptide. Deficiencies in this peptide have now been observed in most patients with narcolepsy, who also have cataplexy. Deficiencies might set off the following chemical responses that may be the cause of narcolepsy:
- Low levels of epinephrine (commonly known as adrenaline), a hormone important in alertness and arousal.
- Changes in the enzyme monoamine oxidase, which is believed to be important in preventing arousal.
- Lower levels of histamine, a chemical that promotes wakefulness.
- Changes in dopamine, an important neurotransmitter (chemical messenger in the brain) that helps regulate sleep.
- Lower levels of leptin, a hormone associated with obesity when levels decline. (People with narcolepsy tend to be overweight.)
- Higher-than-normal secretion of growth hormone during the day, which may play a role in sudden falling-asleep episodes.
- Increase in acetylcholine, which affects REM sleep.