Narcolepsy is a neurological sleep disorder. In people with narcolepsy, the brain has trouble regulating the sleep cycle, resulting in disruptions of normal sleep and wakefulness patterns. The primary symptoms of narcolepsy are excessive daytime sleepiness and cataplexy — sudden, temporary loss of muscle tone. Narcolepsy is a chronic condition, meaning that it is usually lifelong, but it does not usually worsen with age and may improve over time. Narcolepsy is not contagious.
Narcolepsy is caused by biological changes in the brain that interfere with the normal regulation of the sleep-wake cycle. Many cases of narcolepsy are associated with low levels of a brain chemical called hypocretin or orexin, which is necessary for regulating sleep. Research indicates that low hypocretin leads to the “sleep state instability” seen in people with narcolepsy, resulting in daytime sleepiness and disturbed nighttime sleep.
Many factors are believed to play a role in the development of narcolepsy. While narcolepsy is not directly passed down in families in a clear pattern, there are certain genetic variants associated with an increased risk for developing narcolepsy. However, not all people with higher-risk genes develop the sleep disorder. For this reason, most researchers believe that a combination of inherited and environmental factors likely lead some people to develop narcolepsy. Environmental factors may include age, endocrine disorders, and certain infections such as streptococcal pharyngitis, or strep throat.
Evidence suggests narcolepsy may be an autoimmune condition, like multiple sclerosis or lupus, and that hypocretin-producing brain cells (neurons) may be destroyed by immune system attacks.
In secondary narcolepsy, a rare type of narcolepsy, the sleep disorder develops after damage or injury to the brain. Causes of secondary narcolepsy may include brain tumors, head trauma, or multiple sclerosis.
Read more about causes and risk factors for narcolepsy.
The first two mentions of narcolepsy in medical literature were published in 1877 and 1880. In 1877, C. Westphal, a German scientist, wrote about two individuals presenting symptoms of narcolepsy with cataplexy. Westphal described the episodes as “epileptic attacks” and noted the individuals’ sleep attacks. In 1880, French physician Jean-Baptiste-Edouard Gélineau first used the term narcolepsy (narcolepsie in French) to describe symptoms like cataplexy and sleep paralysis. The word narcolepsy comes from the Greek words narkē, meaning “numbness or stupor,” and lepsis, meaning "attack or seizure.” Gélineau was known in his time for treating epilepsy. While Westphal and Gélineau both described cataplexy, that term wasn’t introduced till 1902.
Early understandings of narcolepsy associated the condition with seizure disorders because of cataplexy episodes. Scientific understanding of narcolepsy and all sleep disorders expanded greatly when scientists identified rapid eye movement (REM) sleep in the early 1950s. Some of the earliest modern research into narcolepsy occurred at Stanford University in the early 1960s. During the 1960s and 1970s, researchers at Stanford helped establish sleep medicine as its own field and introduced sleep studies like the overnight polysomnogram and multiple sleep latency test (MSLT).
Research from Japan in the early 1980s opened the door to understanding a possible genetic cause of narcolepsy. Additional research in the next decade found a close association between narcolepsy and the HLA-DQB1*06:02 gene. In 1998, scientists discovered the relationship between hypocretin and narcolepsy. Identifying these two relationships has greatly expanded the scope of research into narcolepsy and its causes, and mechanisms.
Narcolepsy is a rare condition. It affects an estimated 135,000 to 200,000 Americans. It’s believed that about 1 in 2,000 people, or 0.05 percent, have narcolepsy. Actual numbers could be higher because of the number of individuals who haven’t been diagnosed or who have been misdiagnosed. Narcolepsy affects men and women and different ethnic groups equally.
Excessive daytime sleepiness (EDS) is a sensation of exhaustion throughout the day, no matter how much a person has slept at night. EDS is the primary symptom of narcolepsy and occurs in all types of the condition.
Cataplexy is a sudden loss of muscle control, often caused by strong emotions. Cataplexy only occurs in type 1 narcolepsy, previously called narcolepsy with cataplexy. Cateplexy episodes can last for a few seconds to a few minutes. An episode can consist of mild symptoms like eyelid drooping or lead to a serious fall.
Sleep paralysis occurs when a person can’t speak or move either when waking up or falling asleep. Most sleep paralysis episodes only last a few seconds but can occasionally last longer.
Vivid hallucinations can occur when a person with narcolepsy wakes up (hypnopompic hallucinations) and when they fall asleep (hypnagogic hallucinations). Hallucinations that occur in narcolepsy are similar to dreams that would occur during REM sleep, except they occur during a semi-awake state.
Often, people with narcolepsy experience disrupted nighttime sleep, fragmented sleep, or insomnia. Individuals with narcolepsy are able to fall asleep quickly, but may wake frequently throughout the night.
A sleep attack is an inability to stay awake during the day. Sleep attacks are part of the excessive daytime sleepiness that characterizes narcolepsy.
Automatic behaviors occur when a person experiences a brief sleep episode in the middle of an activity. The person continues the activity, but they will not remember what they were doing. Automatic behaviors can be dangerous if they occur while driving.
Narcolepsy can have negative impacts on social involvement, cognition, and mental health, including depression and anxiety. Narcolepsy is also associated with weight gain and precocious puberty.
Learn more about Symptoms of Narcolepsy.
There are three types of narcolepsy — type 1, type 2, and secondary narcolepsy.
Until 2014, type 1 narcolepsy was referred to as narcolepsy with cataplexy. It may still be referred to as narcolepsy with cataplexy in some contexts. Type 1 narcolepsy is distinguished from type 2 narcolepsy by the presence of cataplexy, a sudden loss of muscle tone. Another distinguishing feature of type 1 narcolepsy is low levels of hypocretin. Low hypocretin levels are present in 90 percent of people with type 1 narcolepsy.
Type 2 narcolepsy was previously known as narcolepsy without cataplexy. Unlike individuals with type 1, those with type 2 do not have cataplectic episodes and may or may not have low hypocretin levels. Otherwise, type 1 and 2 narcolepsy share symptoms, including excessive daytime sleepiness, sleep paralysis, and hallucinations.
Secondary narcolepsy is caused by damage or injury to the hypothalamus — the part of the brain that controls sleep function and produces hypocretin. People with secondary narcolepsy share many of the same symptoms as those with types 1 and 2. They will likely also sleep 10 or more hours per day and possibly show signs of neurological damage, including loss of peripheral vision and memory problems.
Narcolepsy is diagnosed through a combination of medical history and diagnostic sleep studies. Unfortunately, diagnostic delays have been common for people with narcolepsy, though improved understanding of the condition is making diagnosis faster.
There are different diagnostic criteria for the different types of narcolepsy, but the diagnostic process may include several elements.
A neurologist or sleep specialist will take a detailed medical history and ask questions about any symptoms of narcolepsy, including excessive daytime sleepiness and cataplexy. Discussing your medical history and symptoms can help your physician determine next steps for diagnosing your condition.
Differential diagnosis is the process of ruling out potential reasons for a set of symptoms. As part of the diagnostic process for narcolepsy, your health care provider may consider other sleep disorders, such as obstructive sleep apnea; other medical conditions; or medications that could cause your symptoms.
A polysomnogram (PSG) is an overnight sleep study used to measure nighttime sleep patterns. The PSG will record brain and muscle activity, eye movement, and breathing.
An MSLT is usually conducted the day after a PSG. The test is used to evaluate excessive daytime sleepiness. You will be asked to take five short naps every couple of hours. The MSLT measures how quickly you fall asleep (known as sleep latency) and the time it takes to enter REM sleep.
Your physician may conduct additional tests in order to diagnose your condition. These include:
Learn more about diagnosing narcolepsy.
Medication options for narcolepsy include treatments approved by the United States Food and Drug Administration (FDA) to treat the condition and others that are used off-label. The right medication for you will likely depend on your specific narcolepsy symptoms. The majority of drugs approved to treat narcolepsy are classified as controlled substances in the U.S. because of their potential for abuse.
The following medications are FDA-approved for narcolepsy:
Xyrem is the only FDA-approved drug for type 1 narcolepsy, or narcolepsy with cataplexy. Side effects can include confusion, dizziness, and headaches. Because of the potential for abuse, Xyrem is only available through a restricted-access enrollment program.
Wakix is approved to treat both excessive daytime sleepiness and cataplexy associated with narcolepsy. Wakix is not scheduled as a controlled substance in the U.S. Side effects of Wakix can include nausea, insomnia, and anxiety.
Sunosi is another medication indicated to treat excessive daytime sleepiness associated with narcolepsy. It is also indicated for obstructive sleep apnea. Common side effects include headaches, dizziness, insomnia, and decreased appetite.
Provigil and Nuvigil are used to improve wakefulness among people with EDS associated with narcolepsy and several other sleep disorders. Headache, nausea, dizziness, and insomnia are common side effects.
Alongside medical treatment, certain lifestyle habits can improve sleep. Here are some recommendations from the National Institute of Neurological Disorders and Stroke:
Treatment for mental health conditions and any conditions related to narcolepsy are both important parts of your narcolepsy treatment plan. Learn more about narcolepsy treatments.
Narcolepsy Condition Guide