What is narcolepsy?
Narcolepsy is a chronic neurological disorder that affects the brain's ability to regulate sleep and wakefulness. It is characterized by excessive daytime sleepiness (EDS), sudden attacks of sleep, and disrupted nocturnal sleep. People with narcolepsy may also experience other symptoms such as sleep paralysis, hallucinations, and cataplexy.
The International Classification of Sleep Disorders, 3rd Edition (ICSD-3), differentiates two subtypes of this sleep disorder (American Academy of Sleep Medicine, 2014):
- Type 1 narcolepsy (formerly known as narcolepsy with cataplexy): This diagnosis is determined either by the presence of low levels of hypocretin, a brain hormone, or by the individual experiencing cataplexy along with excessive daytime sleepiness, as confirmed by a specialized nap test.
- Type 2 narcolepsy (formerly known as narcolepsy without cataplexy): Individuals with this condition experience excessive daytime sleepiness but typically do not have muscle weakness triggered by emotions.
In addition, some rare forms of narcolepsy are autosomal dominant, meaning a person will develop the condition if they inherit a single gene from one parent. These include (MedlinePlus, 2017; Medical News Today, 2022):
- Autosomal dominant cerebral ataxia, deafness, and narcolepsy: This leads to deafness, narcolepsy, and cataplexy. This condition arises in individuals with a mutation in the DNA methyltransferase (DNMT1) gene.
- Autosomal dominant narcolepsy, type 2 diabetes, and obesity: This results in diabetes, obesity, and narcolepsy. This condition also passes from parent to child if the child inherits the single gene responsible from a parent.










