What Causes Narcolepsy?

Exactly what causes narcolepsy is unknown, but researchers have identified several potential triggers of narcolepsy symptoms. Genetics, autoimmune disorders and environmental factors are all possible causes.

Narcolepsy Symptoms and Normal Sleep

An abnormal sleep cycle causes narcolepsy symptoms. Most people enter a period of light non-rapid eye movement (NREM) sleep when they fall asleep. Light NREM sleep gradually transitions into deeper, restful sleep. After deep NREM sleep, the sleep cycle alters again, switching to rapid eye movement (REM) sleep, when most dreaming occurs. During REM sleep the body is temporarily paralyzed to prevent the dreamer from physically acting out dreams.
A person with narcolepsy symptoms has a very different sleep cycle. Upon falling asleep, someone with narcolepsy enters REM sleep within minutes. Narcolepsy symptoms during waking hours have elements of REM sleep stages, such as cataplexy (loss of muscle tone), or vivid dreams or hallucinations.

Does Genetics Cause Narcolepsy?

Narcolepsy can run in families, but genetic factors cannot be considered the sole cause of narcolepsy. According to the University of Maryland (2009), 8 to 10 percent of people with narcolepsy have close relatives who share the disorder.
Narcolepsy symptoms may develop from a combination of genetics and environmental causes of narcolepsy. Possible environmental factors include:
  • Autoimmune disorders
  • Brain injuries
  • Toxins.

Causes of Narcolepsy and Hypocretin Levels

People with narcolepsy symptoms often have low levels of a brain chemical called hypocretin. Hypocretin levels may provide the ultimate answer to what causes narcolepsy.
Hypocretin plays a role in promoting wakefulness, as well as in controlling REM sleep activity. The brain chemical also affects appetite and motor control. This last function is important — narcolepsy symptoms can include a condition called cataplexy. Cataplexy is a loss of motor control and muscle tone. People whose narcolepsy symptoms include cataplexy often have low levels of hypocretin.

Autoimmune Causes of Narcolepsy

It's possible that an autoimmune disease that attacks hypocretin proteins causes narcolepsy. Autoimmune diseases occur when the body mistakenly identifies substances within the body as foreign particles and destroys them. Rheumatoid arthritis and lupus are both autoimmune disorders.
An autoimmune disorder that targets hypocretin would set in motion a chain reaction of events leading to narcolepsy symptoms. Low levels of hypocretin result in less histamine production, a substance that promotes wakefulness. Levels of adrenaline drop, which would increase daytime sleepiness.
At the same time, levels of the chemical acetylcholine rise, which affects REM sleep. Levels of growth hormone, which influence sleepiness, rise as hypocretin levels drop. Low levels of hypocretin may also contribute to chemical imbalances of the brain chemical dopamine and the enzyme monoamine oxidase, both of which affect alertness and sleep.
While not proof that hypocretin deficiencies are causes of narcolepsy, hypocretin deficiencies also reduce leptin levels. Leptin is a hormone associated with obesity. Many people with narcolepsy symptoms are also overweight.

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