Here’s a primer on what’s going on when a person has this condition, as well as its potential causes.
By Definition, Narcolepsy Is When Your Brain Can’t Regulate Sleep and Wake Cycles
Understanding what’s happening physiologically during narcolepsy requires a brief rundown of what happens in your brain and body while you sleep.
For individuals with narcolepsy, these sleep cycles do not follow the typical pattern — and wake cycles can be disrupted, too.
For people with narcolepsy, sleep cycles can occur out of order and suddenly. Many people with narcolepsy enter REM sleep nearly immediately after falling asleep, rather than cycling through the stages of lighter and deeper NREM sleep first — or they experience the muscle weakness or dream activity associated with REM sleep during the day while they’re awake. And because the boundaries between wakefulness and sleep become blurred, people with narcolepsy can experience extremely vivid dreams and hallucinations while falling asleep and waking up.
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There Are Two Types of Narcolepsy That Make Up the Majority of Cases
- Type 1 Narcolepsy People with type 1 narcolepsy (previously called narcolepsy with cataplexy) have either or both of the following: abnormally low levels of a brain hormone called hypocretin (also called orexin, it plays a key role in the ability to stay awake and prevents REM sleep from occurring at the wrong time) and signs of cataplexy (sudden loss of muscle tone and control while you’re awake, which is usually triggered by feeling strong emotions).
- Type 2 Narcolepsy Those who have type 2 narcolepsy (previously called narcolepsy without cataplexy) usually do not have cataplexy and have normal levels of hypocretin, but experience excessive daytime sleepiness (you may nap frequently but feel tired a short time after waking).
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There’s Strong Evidence Narcolepsy May Be an Autoimmune Disorder, Though There May Be Other Causes, Too
While research has revealed a lot about what’s going on when someone has narcolepsy, experts are less clear about what causes someone to develop narcolepsy in the first place.
It’s still less clear what causes the loss of hypocretin in an individual, says Dr. Mignot, who worked on that seminal narcolepsy research at Stanford. “There is extremely strong evidence that it’s an autoimmune disease.”
Editorial Sources and Fact-Checking
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Sources
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- Narcolepsy Fast Facts. Narcolepsy Network.
- Understanding Narcolepsy. Harvard Medical School Division of Sleep Medicine.
- Narcolepsy: Symptoms and Causes. Mayo Clinic.
- Brain Basics: Understanding Sleep. National Institute of Neurological Disorders and Stroke.
- International Classification of Sleep Disorders – Third Edition. American Academy of Sleep Medicine.
- Narcolepsy. StatPearls.
- The Sleep Disorder Canine Narcolepsy Is Caused by a Mutation in the Hypocretin (Orexin) Receptor 2 Gene. Cell.
- Narcolepsy in Orexin Knockout Mice. Cell.
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- Challenges in Diagnosing Narcolepsy Without Cataplexy: A Consensus Statement. Sleep.
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Resources
- Narcolepsy. National Institute of Neurological Disorders and Stroke. January 20, 2023
- Narcolepsy Fast Facts. Narcolepsy Network. June 2015.
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- Narcolepsy: Symptoms and Causes. Mayo Clinic. January 14, 2023.
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- Ahmed SS, Volkmuth W, Duca J, et al. Antibodies to Influenza Nucleoprotein Cross-React With Human Hypocretin Receptor 2. Science Translational Medicine. July 1, 2015.
- Lin L, Faraco J, Li R, et al. The Sleep Disorder Canine Narcolepsy Is Caused by a Mutation in the Hypocretin (Orexin) Receptor 2 Gene [PDF]. Cell. August 6, 1999.
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