Narcolepsy 

U.S. DEPARTMENT OF HEALTH

AND HUMAN SERVICES

National Institutes of Health

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Narcolepsy 

What is narcolepsy?

Narcolepsy is a chronic neurological disorder 

that affects the brain’s ability to control 

sleep-wake cycles. People with narcolepsy 

usually feel rested after waking, but then feel 

very sleepy throughout much of the day. Many 

individuals with narcolepsy also experience 

uneven and interrupted sleep that can involve 

waking up frequently during the night. 

Narcolepsy can greatly affect daily activities. 

People may unwillingly fall asleep even if they 

are in the middle of an activity like driving, 

eating, or talking. Other symptoms may include 

sudden muscle weakness while awake that makes 

a person go limp or unable to move (cataplexy), 

vivid dream-like images or hallucinations, and 

total paralysis just before falling asleep or just 

after waking up (sleep paralysis). 

In a normal sleep cycle, a person enters 

rapid eye movement (REM) sleep after 

about 60 to 90 minutes. Dreams occur during 

REM sleep, and the brain keeps muscles limp 

during this sleep stage, which prevents people 

from acting out their dreams. People with 

narcolepsy frequently enter REM sleep rapidly, 

within 15 minutes of falling asleep. Also, the 

muscle weakness or dream activity of REM 
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sleep can occur during wakefulness or be 

absent during sleep. This helps explain some 

symptoms of narcolepsy. 

If left undiagnosed or untreated, narcolepsy 

can interfere with psychological, social, and 

cognitive function and development and can 

inhibit academic, work, and social activities.

Who is most at risk for narcolepsy?

Narcolepsy affects both males and females 

equally. Symptoms often start in childhood, 

adolescence, or young adulthood (ages 7 to 25), 

but can occur at any time in life. It is estimated 

that anywhere from 135,000 to 200,000 people 

in the United States have narcolepsy. However, 

since this condition often goes undiagnosed, 

the number may be higher. Since people with 

narcolepsy are often misdiagnosed with other 

conditions, such as psychiatric disorders or 

emotional problems, it can take years for 

someone to get the proper diagnosis. 

What are the symptoms?

Narcolepsy is a lifelong problem, but it does 

not usually worsen as the person ages. 

Symptoms can partially improve over time, 

but they will never disappear completely. 

The most typical symptoms are excessive 

daytime sleepiness, cataplexy, sleep paralysis, 

and hallucinations. Though all have excessive 

daytime sleepiness, only 10 to 25 percent of 

affected individuals will experience all of 

the other symptoms during the course of 

their illness.
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• Excessive daytime sleepiness (EDS). All 

individuals with narcolepsy have EDS, and 

it is often the most obvious symptom. EDS 

is characterized by persistent sleepiness, 

regardless of how much sleep an individual 

gets at night. However, sleepiness in 

narcolepsy is more like a “sleep attack”, where 

an overwhelming sense of sleepiness comes on 

quickly. In between sleep attacks, individuals 

have normal levels of alertness, particularly if 

doing activities that keep their attention.

• Cataplexy. This sudden loss of muscle tone 

while a person is awake leads to weakness and 

a loss of voluntary muscle control. It is often 

triggered by sudden, strong emotions such 

as laughter, fear, anger, stress, or excitement. 

The symptoms of cataplexy may appear weeks 

or even years after the onset of EDS. Some 

people may only have one or two attacks in a 

lifetime, while others may experience many 

attacks a day. In about 10 percent of cases of 

narcolepsy, cataplexy is the first symptom to 

appear and can be misdiagnosed as a seizure 

disorder. Attacks may be mild and involve only 

a momentary sense of minor weakness in a 

limited number of muscles, such as a slight 

drooping of the eyelids. The most severe attacks 

result in a total body collapse during which 

individuals are unable to move, speak, or keep 

their eyes open. But even during the most 

severe episodes, people remain fully conscious, 

a characteristic that distinguishes cataplexy 

from fainting or seizure disorders. The loss 

of muscle tone during cataplexy resembles 
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paralysis of muscle activity that naturally 

occurs during REM sleep. Episodes last a few 

minutes at most and resolve almost instantly 

on their own. While scary, the episodes are 

not dangerous as long as the individual finds a 

safe place in which to collapse. 

• Sleep paralysis. The temporary inability to 

move or speak while falling asleep or waking 

up usually lasts only a few seconds or minutes 

and is similar to REM-induced inhibitions 

of voluntary muscle activity. Sleep paralysis 

resembles cataplexy except it occurs at the edges 

of sleep. As with cataplexy, people remain fully 

conscious. Even when severe, cataplexy and sleep 

paralysis do not result in permanent dysfunction

—after episodes end, people rapidly recover 

their full capacity to move and speak.

• Hallucinations. Very vivid and sometimes 

frightening images can accompany sleep 

paralysis and usually occur when people are 

falling asleep or waking up. Most often the 

content is primarily visual, but any of the 

other senses can be involved. 

Additional symptoms of narcolepsy include:

• Fragmented sleep and insomnia. While 

individuals with narcolepsy are very sleepy 

during the day, they usually also experience 

difficulties staying asleep at night. Sleep may 

be disrupted by insomnia, vivid dreaming, 

sleep apnea, acting out while dreaming, and 

periodic leg movements.

• Automatic behaviors. Individuals with 

narcolepsy may experience temporary sleep 

episodes that can be very brief, lasting no 
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more than seconds at a time. A person falls 

asleep during an activity (e.g., eating, talking) 

and automatically continues the activity for 

a few seconds or minutes without conscious 

awareness of what they are doing. This 

happens most often while people are engaged 

in habitual activities such as typing or driving. 

They cannot recall their actions, and their 

performance is almost always impaired. Their 

handwriting may, for example, degenerate 

into an illegible scrawl, or they may store 

items in bizarre locations and then forget 

where they placed them. If an episode occurs 

while driving, individuals may get lost or 

have an accident. People tend to awaken 

from these episodes feeling refreshed, 

finding that their drowsiness and fatigue 

has temporarily subsided.

What are the types of narcolepsy?

There are two major types of narcolepsy: 

• Type 1 narcolepsy (previously termed 

narcolepsy with cataplexy). This diagnosis 

is based on the individual either having low 

levels of a brain hormone (hypocretin) or 

reporting cataplexy and having excessive 

daytime sleepiness on a special nap test.

• Type 2 narcolepsy (previously termed 

narcolepsy without cataplexy). People with 

this condition experience excessive daytime 

sleepiness but usually do not have muscle 

weakness triggered by emotions. They 

usually also have less severe symptoms 

and have normal levels of the brain 

hormone hypocretin.
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A condition known as secondary narcolepsy 

can result from an injury to the hypothalamus, 

a region deep in the brain that helps regulate 

sleep. In addition to experiencing the typical 

symptoms of narcolepsy, individuals may also 

have severe neurological problems and sleep for 

long periods (more than 10 hours) each night.

What causes narcolepsy?

Narcolepsy may have several causes. 

Nearly all people with narcolepsy who 

have cataplexy have extremely low levels of 

the naturally occurring chemical hypocretin, 

which promotes wakefulness and regulates 

REM sleep. Hypocretin levels are usually 

normal in people who have narcolepsy 

without cataplexy. 

Although the cause of narcolepsy is not 

completely understood, current research 

suggests that narcolepsy may be the result 

of a combination of factors working 

together to cause a lack of hypocretin. 

These factors include: 

• Autoimmune disorders. When cataplexy 

is present, the cause is most often the loss 

of brain cells that produce hypocretin. 

Although the reason for this cell loss 

is unknown, it appears to be linked to 

abnormalities in the immune system. 

Autoimmune disorders occur when the 

body’s immune system turns against 

itself and mistakenly attacks healthy 

cells or tissue. Researchers believe that 
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in individuals with narcolepsy, the body’s 

immune system selectively attacks the 

hypocretin-containing brain cells because 

of a combination of genetic and 

environmental factors.

• Family history. Most cases of narcolepsy 

are sporadic, meaning the disorder occurs 

in individuals with no known family 

history. However, clusters in families 

sometimes occur—up to 10 percent of 

individuals diagnosed with narcolepsy 

with cataplexy report having a close 

relative with similar symptoms.

• Brain injuries. Rarely, narcolepsy results 

from traumatic injury to parts of the brain 

that regulate wakefulness and REM sleep 

or from tumors and other diseases in the 

same regions.

How is narcolepsy diagnosed?

A clinical examination and detailed medical 

history are essential for diagnosis and 

treatment of narcolepsy. Individuals may be 

asked by their doctor to keep a sleep journal 

noting the times of sleep and symptoms over 

a one- to two-week period. Although none of 

the major symptoms are exclusive to narcolepsy, 

cataplexy is the most specific symptom and 

occurs in almost no other diseases. 

A physical exam can rule out or identify 

other neurological conditions that may be 

causing the symptoms. Two specialized tests, 

which can be performed in a sleep disorders 
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clinic, are required to establish a diagnosis 

of narcolepsy:

• Polysomnogram (PSG or sleep study).

The PSG is an overnight recording of brain 

and muscle activity, breathing, and eye 

movements. A PSG can help reveal whether 

REM sleep occurs early in the sleep cycle 

and if an individual’s symptoms result from 

another condition such as sleep apnea.

• Multiple sleep latency test (MSLT).

The MSLT assesses daytime sleepiness by 

measuring how quickly a person falls asleep 

and whether they enter REM sleep. On the 

day after the PSG, an individual is asked to 

take five short naps separated by two hours 

over the course of a day. If an individual 

falls asleep in less than 8 minutes on average 

over the five naps, this indicates excessive 

daytime sleepiness. However, individuals 

with narcolepsy also have REM sleep start 

abnormally quickly. If REM sleep happens 

within 15 minutes at least two times out of 

the five naps and the sleep study the night 

before, this is likely an abnormality caused 

by narcolepsy. 

Occasionally, it may be helpful to measure the 

level of hypocretin in the fluid that surrounds 

the brain and spinal cord. To perform this 

test, a doctor will withdraw a sample of the 

cerebrospinal fluid using a lumbar puncture 

(also called a spinal tap) and measure the 

level of hypocretin-1. In the absence of 

other serious medical conditions, low 

hypocretin-1 levels almost certainly 

indicate type 1 narcolepsy. 
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What treatments are available?

Although there is no cure for narcolepsy, 

some of the symptoms can be treated 

with medicines and lifestyle changes. 

When cataplexy is present, the loss of 

hypocretin is believed to be irreversible 

and lifelong. Excessive daytime sleepiness 

and cataplexy can be controlled in most 

individuals with medications. 

Medications 

• Modafinil. The initial line of treatment 

is usually a central nervous system 

stimulant such as modafinil. Modafinil 

is usually prescribed first because it is 

less addictive and has fewer side effects 

than older stimulants. For most people 

these drugs are generally effective at 

reducing daytime drowsiness and 

improving alertness. 

• Amphetamine-like stimulants. In cases 

where modafinil is not effective, doctors 

may prescribe amphetamine-like stimulants 

such as methylphenidate to alleviate EDS. 

However, these medications must be 

carefully monitored because they can 

have such side effects as irritability and 

nervousness, shakiness, disturbances 

in heart rhythm, and nighttime sleep 

disruption. In addition, health care 

professionals should be careful when 

prescribing these drugs and people 

should be careful using them because the 

potential for abuse is high with 

any amphetamine.
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• Antidepressants. Two classes of 

antidepressant drugs have proven effective 

in controlling cataplexy in many individuals: 

tricyclics (including imipramine, desipramine, 

clomipramine, and protriptyline) and 

selective serotonin and noradrenergic 

reuptake inhibitors (including venlafaxine, 

fluoxetine, and atomoxetine). In general, 

antidepressants produce fewer adverse effects 

than amphetamines. However, troublesome 

side effects still occur in some individuals, 

including impotence, high blood pressure, 

and heart rhythm irregularities. 

• Sodium oxybate. Sodium oxybate (also 

known as gamma hydroxybutyrate or GHB) 

has been approved by the U.S. Food and 

Drug Administration to treat cataplexy and 

excessive daytime sleepiness in individuals 

with narcolepsy. It is a strong sedative that 

must be taken twice a night. Due to safety 

concerns associated with the use of this 

drug, the distribution of sodium oxybate 

is tightly restricted. 

Lifestyle changes

Not everyone with narcolepsy can consistently 

maintain a fully normal state of alertness using 

currently available medications. Drug therapy 

should accompany various lifestyle changes. 

The following strategies may be helpful: 

• Take short naps. Many individuals take 

short, regularly scheduled naps at times 

when they tend to feel sleepiest.
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• Maintain a regular sleep schedule.

Going to bed and waking up at the same 

time every day, even on the weekends, 

can help people sleep better. 

• Avoid caffeine or alcohol before bed.

Individuals should avoid alcohol and 

caffeine for several hours before bedtime. 

• Avoid smoking, especially at night. 

• Exercise daily. Exercising for at least 

20 minutes per day at least 4 or 5 hours 

before bedtime also improves sleep quality 

and can help people with narcolepsy avoid 

gaining excess weight.

• Avoid large, heavy meals right before 

bedtime. Eating very close to bedtime can 

make it harder to sleep. 

• Relax before bed. Relaxing activities such 

as a warm bath before bedtime can help 

promote sleepiness. Also make sure the 

sleep space is cool and comfortable.

Safety precautions, particularly when driving, 

are important for everyone with narcolepsy. 

People with untreated symptoms are more 

likely to be involved in automobile accidents 

although the risk is lower among individuals 

who are taking appropriate medication. 

EDS and cataplexy can lead to serious 

injury or death if left uncontrolled. Suddenly 

falling asleep or losing muscle control can 

transform actions that are ordinarily safe, 

such as walking down a long flight of stairs, 

into hazards. 
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The Americans with Disabilities Act 

requires employers to provide reasonable 

accommodations for all employees with 

disabilities. Adults with narcolepsy can 

often negotiate with employers to modify 

their work schedules so they can take 

naps when necessary and perform their 

most demanding tasks when they are 

most alert. Similarly, children and 

adolescents with narcolepsy may be able 

to work with school administrators to 

accommodate special needs, like taking 

medications during the school day, 

modifying class schedules to fit in a 

nap, and other strategies.

Additionally, support groups can be extremely 

beneficial for people with narcolepsy who 

want to develop better coping strategies or 

feel socially isolated due to embarrassment 

about their symptoms. Support groups also 

provide individuals with a network of social 

contacts who can offer practical help and 

emotional support.

What is the state of the science 

involving narcolepsy?

I

n the past few decades, scientists have made 

considerable progress in understanding 

narcolepsy and identifying genes strongly 

associated with the disorder. 

Groups of neurons in several parts of the 

brain interact to control sleep, and the activity 

of these neurons is controlled by a large number 
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of genes. The loss of hypocretin-producing 

neurons in the hypothalamus is the primary 

cause of type 1 narcolepsy. These neurons are 

important for stabilizing sleep and wake states. 

When these neurons are gone, changes between 

wake, REM sleep, and non-REM sleep can 

happen spontaneously. This results in the sleep 

fragmentation and daytime symptoms that 

people with narcolepsy experience.

It remains unclear exactly why hypocretin 

neurons die. However, research increasingly 

points to immune system abnormalities. 

HLA—human leukocyte antigen—genes 

play an important role in regulating the 

immune system. This gene family provides 

instructions for making a group of related 

proteins called the HLA complex, which 

helps the immune system distinguish between 

good proteins from an individual’s own body 

and bad ones made by foreign invaders like 

viruses and bacteria. One of the genes in this 

family is HLA-DQB1. A variation in this 

gene, called HLA-DQB1*06:02, increases the 

chance of developing narcolepsy, particularly 

the type of narcolepsy with cataplexy and a 

loss of hypocretins (also known as orexins). 

HLA-DQB1*06:02 and other HLA gene 

variations may increase susceptibility to 

an immune attack on hypocretin neurons, 

causing these cells to die. Most people with 

narcolepsy have this gene variation and may 

also have specific versions of closely related 

HLA genes. 
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However, it is important to note that these 

gene variations are common in the general 

population and only a small portion of the 

people with the HLA-DQB1*06:02 variation 

will develop narcolepsy. This indicates that 

other genetic and environmental factors are 

important in determining if an individual 

will develop the disorder.

Narcolepsy follows a seasonal pattern and is 

more likely to develop in the spring and early 

summer after the winter season, a time when 

people are more likely to get sick. By studying 

people soon after they develop the disorder, 

scientists have discovered that individuals with 

narcolepsy have high levels of anti-streptolysin 

O antibodies, indicating an immune response 

to a recent bacterial infection such as strep 

throat. Also, the H1N1 influenza epidemic 

in 2009 resulted in a large increase in the 

number of new cases of narcolepsy. Together, 

this suggests that individuals with the 

HLA-DQB1*06:02 variation are at risk 

for developing narcolepsy after they are 

exposed to a specific trigger, like certain 

infections that trick the immune system 

to attack the body.

What research is being done?

The mission of the National Institute 

of Neurological Disorders and Stroke 

(NINDS) is to seek fundamental knowledge 

about the brain and nervous system and to 

use that knowledge to reduce the burden 

of neurological disease. The NINDS is a 
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component of the National Institutes of 

Health (NIH), the leading supporter of 

biomedical research in the world.

The NINDS, along with several other NIH 

Institutes and Centers, supports research on 

narcolepsy and other sleep disorders through 

grants to medical institutions across the 

country. Additionally, the NIH’s National 

Heart, Lung, and Blood Institute manages 

the National Center on Sleep Disorders 

Research (NCSDR), which coordinates 

Federal government sleep research activities, 

promotes doctoral and postdoctoral training 

programs, and educates the public and health 

care professionals about sleep disorders. For 

more information, visit the NCSDR website 

at www.nhlbi.nih.gov/about/org/ncsdr/.

Genetics and biochemicals

NINDS-sponsored researchers are conducting 

studies devoted to further clarifying the 

wide range of genetic—both HLA genes 

and non-HLA genes—and environmental 

factors that may cause narcolepsy. Other 

investigators are using animal models to 

better understand hypocretin and other 

chemicals such as glutamate that may play a 

key role in regulating sleep and wakefulness. 

Researchers are also investigating wakepromoting compounds to widen the range 

of available therapeutic options and create 

treatment options that reduce undesired 

side effects and decrease the potential for 

abuse. A greater understanding of the 
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complex genetic and biochemical bases of 

narcolepsy will eventually lead to new therapies 

to control symptoms and may lead to a cure. 

Immune system 

Abnormalities in the immune system may 

play an important role in the development of 

narcolepsy. NINDS-sponsored scientists have 

demonstrated the presence of unusual immune 

system activity in people with narcolepsy. 

Further, strep throat and certain varieties of 

influenza are now thought to be triggers in 

some at-risk individuals. Other NINDS 

researchers are also working to understand 

why the immune system destroys hypocretin 

neurons in narcolepsy in the hopes of finding 

a way to prevent or cure the disorder. 

Sleep biology

The NINDS continues to support investigations 

into the basic biology of sleep, such as 

examining the brain mechanisms involved 

in generating and regulating REM sleep 

and other sleep behaviors. Since sleep and 

circadian rhythms are controlled by networks 

of neurons in the brain, NINDS researchers 

are also examining how neuronal circuits 

function in the body and contribute to sleep 

disorders like narcolepsy. A more comprehensive 

understanding of the complex biology of sleep 

will give scientists a better understanding of 

the processes that underlie narcolepsy and 

other sleep disorders.
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How can I help research?

The NINDS supports the NIH NeuroBioBank, 

a national resource for investigators using 

human post-mortem brain tissue and related 

biospecimens for their research to understand 

conditions of the nervous system. The 

NeuroBioBank serves as a central point of 

access to collections that span neurological, 

neuropsychiatric, and neurodevelopmental 

diseases and disorders. Tissue from individuals 

with narcolepsy is needed to enable scientists to 

study this disorder more intensely. Participating 

groups include brain and tissue repositories, 

researchers, NIH program staff, information 

technology experts, disease advocacy groups, 

and, most importantly, individuals seeking 

information about opportunities to donate. 

More information about NeuroBioBank and 

opportunities to donate tissue is available at 

https://neurobiobank.nih.gov/.

Additionally, the NINDS supports genetic 

and immunological research in narcolepsy 

at Stanford University. Blood samples from 

individuals with narcolepsy can be sent by 

mail and are needed to enable scientists to study 

this disorder more intensely. Prospective donors 

may contact: 

Stanford University Center for Narcolepsy

450 Broadway Street

M/C 5704

Redwood City, CA 94063

650-721-7574

https://med.stanford.edu/narcolepsy.html
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Where can I get more information?

For more information on neurological disorders 

or research programs funded by the National 

Institute of Neurological Disorders and Stroke, 

contact the Institute’s Brain Resources and 

Information Network (BRAIN) at: 

BRAIN

P.O. Box 5801

Bethesda, MD 20824

800-352-9424

www.ninds.nih.gov

Information is also available from the following 

organizations:

Narcolepsy Network

46 Union Drive #A212

North Kingstown, RI 02852

401-667-2523

888-292-6522

www.narcolepsynetwork.org

National Sleep Foundation

1010 N. Glebe Road, Suite 420

Arlington, VA 22201

703-243-1697

www.sleepfoundation.org

Wake Up Narcolepsy

P.O. Box 60293

Worcester, MA 01606

978-751-3693

www.wakeupnarcolepsy.org
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National Heart, Lung, and Blood Institute 

(NHLBI) Health Information Center

National Institutes of Health/DHHS

P.O. Box 30105

Bethesda, MD 20824-0105

301-592-8573

800-575-9355 

www.nhlbi.nih.gov

U.S. National Library of Medicine 

National Institutes of Health/DHHS

8600 Rockville Pike

Bethesda, MD 20894

301-594-5983

888-346-3656

www.nlm.nih.gov

American Sleep Association 

1002 Lilitz Pike, Suite 229

Lilitz, PA 17543

www.sleepassociation.org


NIH . . . Turning Discovery Into Health

Prepared by:

Office of Communications and Public Liaison

National Institute of Neurological 

Disorders and Stroke

National Institutes of Health

Department of Health and Human Services

Bethesda, Maryland 20892-2540

NIH Publication No. 17-1637 May 2017