Many cases of narcolepsy are thought to be caused by a lack of the brain chemical orexin (also known as hypocretin), which regulates sleep.

This deficiency is thought to result from the immune system mistakenly attacking parts of the brain that produce this chemical.

However, this is not the cause in all cases.

Problem with the immune system

Normally, antibodies (proteins) are released by the body to destroy disease-carrying organisms and toxins. When antibodies mistakenly attack healthy cells and tissue, it’s known as an “autoimmune response”.

In 2010, scientists in Switzerland discovered that some people with narcolepsy produce trib 2 antibodies, which attack the orexin-producing areas of their brain. This results in a lack of orexin, and their brain not being able to regulate sleep cycles.

These research results help explain the cause of narcolepsy in many cases, but it doesn’t explain why some people with the condition still produce near-normal levels of orexin.

Possible triggers

A number of factors may increase a person’s risk of narcolepsy or cause an autoimmune problem, including:

• an inherited genetic fault
• hormonal changes, including those that occur in puberty or the menopause
• major psychological stress
• a sudden change in sleep patterns
• an infection, such as flu or a streptococcal infection
• having the flu vaccine Pandemrix (see below)

Research has yet to confirm whether all of these play a role in narcolepsy.

Pandemrix vaccine

Recent research has shown that there is an association between the use of the flu vaccine Pandemrix, which was used during the swine flu epidemic of 2009-10, and narcolepsy in children.

This risk is very small: researchers estimated the chance of developing narcolepsy after receiving a dose of the vaccine in the UK to be around 1 in 52,000.

However, as a result, Pandemrix is no longer given to people under the age of 20.

Impact of narcolepsy on sleep

The total time someone with narcolepsy spends sleeping is not necessarily different to that of people without the condition.

However, narcolepsy can significantly affect sleep cycles and quality of sleep.

Sleep consists of periods of different brain activity known as non-rapid eye movement (NREM) and rapid eye movement (REM). REM sleep is when brain activity starts to increase and dreaming may occur.

Most people go through several sleep cycles that consist of four stages of NREM sleep at first, followed by a short period of REM sleep.

If you have narcolepsy, this pattern is much more fragmented, and you may wake several times during the night. You may also experience REM sleep much earlier than normal after falling asleep, and you may experience effects of REM sleep, such as dreaming and paralysis, while you are still conscious.

Narcolepsy can usually be diagnosed by observing how you sleep and by ruling out other conditions.

If you think you may have narcolepsy, you should see your GP. Before your appointment, it may be useful to record your symptoms in a diary or complete an Epworth sleepiness questionnaire (see below).

Your GP will take a close look at your medical and family history. They will ask about your sleeping habits and any other symptoms you are experiencing.

Ruling out other conditions

Narcolepsy can sometimes be difficult to diagnose because the symptoms may be attributed to other conditions, such as sleep apnoea, epilepsy, depression, an underactive thyroid gland (hypothyroidism) or a previous head injury.

Excessive daytime sleepiness can also sometimes be caused by the side effects of certain medications.

Therefore, your GP may carry out several tests to try and rule out any other conditions that may be causing your symptoms. For example, you may have a physical examination, blood pressure tests and blood tests.

Sleep analysis

If your GP thinks you may have narcolepsy, they will refer you to a specialist in sleep disorders, who will analyse your sleep patterns. There are many different ways your sleep can be analysed.

Epworth sleepiness scale

The Epworth sleepiness scale is a questionnaire used to help analyse situations that make you feel sleepy. Your GP will use the results of your completed questionnaire to decide whether to refer you to a sleep specialist.

When you fill out the questionnaire, you will be asked to rank the likelihood that you will fall asleep in situations such as sitting and reading, watching television and travelling as a passenger in a car.

A score of 10 or below indicates you have a level of daytime sleepiness equal to the general population. A score of 18 or above indicates you have a high level of daytime sleepiness. If this is the case, your GP will probably refer you to a sleep specialist for further investigation.

An online version of the Epworth sleepiness scale is available on the Narcolepsy UK website.

Polysomnography

Polysomnography is an investigation of your sleep, carried out at a specialist sleep centre. The study usually involves staying overnight at the sleep centre so your sleeping patterns can be analysed.

During the night, several different parts of your body will be carefully monitored while you sleep using electrodes (small metallic discs) and bands on the surface of your skin and around parts of your body. Sensors will also be placed on your legs and an oxygen sensor attached to your finger.

A number of different tests will be carried out during polysomnography, including:

• electroencephalography (EEG) – which monitors brain waves
• electromyography (EMG) – which monitors muscle tone
• recordings of movements in your chest and abdomen
• recordings of airflow through your mouth and nose
• pulse oximetry – which measures your heart rate and blood oxygen levels
• electrocardiography (ECG) – which monitors your heart

Sound recording and video equipment may also be used to record sound and images.

After you have slept, a specialist will analyse your test results to determine whether you have normal brain wave activity, breathing patterns, and muscle and eye movement.

Multiple sleep latency test

A multiple sleep latency test measures how long it takes for you to fall asleep during the day. You may have this test after polysomnography.

For the test, you will be asked to take several naps throughout the day, and a specialist will analyse how quickly and easily you fall asleep.

If you have narcolepsy, you will usually fall asleep easily and enter rapid eye movement (REM) sleep very quickly.

Measuring orexin (hypocretin) levels

Many cases of narcolepsy are linked to a deficiency in the sleep-regulating brain chemical orexin (also known as hypocretin).

Recent research has shown that measuring the level of orexin in your cerebrospinal fluid (which surrounds the brain and spinal cord) can be useful in diagnosing narcolepsy, and this test is increasingly being used by sleep disorder specialists to help make a diagnosis.

To measure your level of orexin, a sample of your cerebrospinal fluid is removed using a needle during a procedure called a lumbar puncture.

Narcolepsy is a rare, long-term brain disorder that causes a person to suddenly fall asleep at inappropriate times.

The brain is unable to regulate sleeping and waking patterns normally, which can result in:

• excessive daytime sleepiness – feeling very drowsy throughout the day, and having difficulty concentrating and staying awake
• sleep attacks – falling asleep suddenly and without warning
• cataplexy – temporary loss of muscle control, often in response to emotions such as laughter and anger
• sleep paralysis – a temporary inability to move or speak when waking up or falling asleep

Narcolepsy should not cause serious or long-term physical health problems, but it can have a significant impact on daily life and can be difficult to cope with emotionally.

Read more about the symptoms of narcolepsy.

What causes narcolepsy?

Many cases of narcolepsy are caused by a lack of the brain chemical orexin (also known as hypocretin), which regulates sleep.

This deficiency is thought to result from the immune system mistakenly attacking parts of the brain that produce this chemical.

However, this does not explain all cases of narcolepsy, and the exact cause of this problem is often unclear.

Factors that have been suggested to trigger narcolepsy include hormonal changes (which can occur during puberty or the menopause), major psychological stress, a sudden change in sleep patterns and an infection (such as flu).

Read more about the causes of narcolepsy.

Who is affected

Narcolepsy is a fairly rare condition. It is difficult to know exactly how many people have narcolepsy because many cases are thought to go unreported. However, it is estimated that the condition affects at least 25,000 people in the UK.

Men and women are thought to be affected equally by narcolepsy, although some studies have suggested the condition may be more common in men. The symptoms often begin during adolescence, although the condition is usually diagnosed between the ages of 20 and 40.

How narcolepsy is diagnosed

You should make an appointment to see your GP if you think you may have narcolepsy.

Your GP may ask about your sleeping habits and any other symptoms you have. They may then carry out tests to help rule out other conditions that could be causing your excessive daytime sleepiness, such as sleep apnoea or an underactive thyroid gland (hypothyroidism).

If necessary, you will be referred to a specialist in sleep disorders, who will analyse your sleep patterns. This will usually involve staying overnight in a specialist sleep centre so various aspects of your sleep can be monitored.

Read more about diagnosing narcolepsy.

How narcolepsy is treated

There is currently no cure for narcolepsy, but making changes to improve your sleeping habits and taking medication can help minimise the impact the condition has on your daily life.

Taking frequent, brief naps evenly spaced throughout the day is one of the best ways to manage excessive daytime drowsiness. This may be difficult when you are at work or school, but your GP or specialist may be able to devise a sleep schedule that will help you get into a routine of taking naps.

Keeping to a strict bedtime routine can also help, so you should go to bed at the same time each night whenever possible.

If your symptoms are particularly troublesome, you may be prescribed medication that can help reduce daytime sleepiness, prevent cataplexy attacks and improve your sleep at night. These medications are usually taken as daily tablets, capsules or drinkable solutions.

Read more about treating narcolepsy.

Not everyone with narcolepsy will experience the same symptoms. Some experience them regularly, while others are less frequently affected.

Symptoms may develop slowly over a number of years, or suddenly over the course of a few weeks.

Narcolepsy is generally a long-term (chronic) condition, although some of the symptoms may improve as you get older.

You should make an appointment to see your GP if you think you may have narcolepsy, so they can determine what is causing your symptoms. If necessary, you will be referred to a specialist in sleep disorders, who can confirm the diagnosis. Read more about diagnosing narcolepsy.

Excessive daytime sleepiness

In most cases, excessive daytime sleepiness is the first sign of narcolepsy. This can have a significant impact on everyday life.

Feeling drowsy throughout the day and struggling to stay awake makes it difficult to concentrate at work or school. People with narcolepsy may be misjudged as being lazy or rude.

Sleep attacks

Sleep attacks – falling asleep suddenly and without warning – are also common in people with narcolepsy. They often occur after eating, although can happen at any time.

The length of time a sleep attack lasts will vary from person to person. Some people will only have “microsleeps” lasting a few seconds, whereas others may fall asleep for several minutes.

If narcolepsy is not well controlled, sleep attacks may happen several times a day.

Cataplexy

Most people who have narcolepsy also experience cataplexy – sudden, temporary muscle weakness or loss of muscular control. Typical symptoms are:

• the jaw dropping
• the head slumping down
• legs collapsing uncontrollably
• slurred speech 
• finding it difficult to focus, or double vision

Cataplexy attacks are usually triggered by an emotion, such as excitement, laughter, anger or surprise. Attacks can last from a few seconds to several minutes.

Some people with narcolepsy have cataplexy attacks once or twice a year, while others experience them several times a day. In an attempt to avoid attacks, some people may become emotionally withdrawn and socially isolated.

Sleep paralysis

Some people with narcolepsy will experience episodes of sleep paralysis. This is a temporary inability to move or speak that occurs when you are waking up or falling asleep.

The episodes can last from a few seconds to several minutes. Although sleep paralysis does not cause any harm, being unable to move can be frightening.

Other symptoms

As well as the symptoms described above, narcolepsy can cause a number of other symptoms, including:

• hallucinations – seeing or hearing things that are not real, particularly when going to sleep or waking up
• memory problems
• headaches
• restless sleep – for example, having hot flushes, waking up frequently, having vivid nightmares or physically acting out dreams
• automatic behaviour – carrying on with an activity, but having no recollection of it afterwards 
• depression

If you have narcolepsy and it is making you feel depressed or low, speak to your GP.

They can give advice on how to minimise the effect narcolepsy has on your daily life. They can also put you in touch with a narcolepsy organisation or support group, such as Narcolepsy UK.

There is no specific cure for narcolepsy, but you can manage the symptoms and minimise their impact on your daily life.

In mild cases, making some simple changes to your sleeping habits can help. If the symptoms are more severe, you will usually need to take medication.

Good sleeping habits

There are steps you can take to reduce excessive daytime sleepiness and make it easier to sleep at night, including:

• taking frequent, brief naps evenly spaced throughout the day – your GP or sleep specialist can help you plan a schedule that fits in with your other activities
• sticking to a strict bedtime routine – aim go to bed and wake up at the same time every day when possible
• trying to relax before going to bed – for example, by having a warm bath
• keeping the area where you sleep a comfortable temperature, quiet and free of distractions
• avoiding caffeine (found in tea, coffee and some fizzy drinks), alcohol and smoking before going to bed
• exercising regularly, but stopping several hours before you go to bed
• not eating large, heavy meals before going to bed

Some over-the-counter (OTC) medications, such as cold and allergy medicines, can cause drowsiness as a side effect. Therefore, if you have narcolepsy, avoid taking these types of medicines during the day because they may make your daytime drowsiness worse.

Speak to your GP or pharmacist if you are unsure which medicines cause drowsiness. They may be able to recommend non-drowsy alternatives.

Talking to others

As well as being a difficult condition to live with, narcolepsy can be a difficult condition for others to understand. Some of the symptoms, such as cataplexy (sudden loss of muscle control), can also be frightening for people who are unaware of the condition. Therefore, you may find it useful to talk to your friends and family about your condition.

If your child has been diagnosed with narcolepsy, you should inform their school. It’s important that teachers are aware of the diagnosis so they do not mistake your child’s behaviour as laziness or staying up too late at night.

Your GP or specialist may be able to arrange for you to speak to a social worker if they think it may help. A social worker can offer counselling and support – including advice about careers, any adjustments that can be made at school or work, and any financial or relationship problems you may be having.

You might also find it useful to contact a local or national narcolepsy support group, such as Narcolepsy UK. These groups can offer advice about living with the condition and can put you in touch with other people in a similar situation.

Medication

A number of different medications are used to treat the symptoms of narcolepsy, although these are not all licensed for narcolepsy, and the evidence for their effectiveness in treating the condition is not always strong.

The availability of some of these medications on the NHS can also differ, depending on the policy of your local NHS authority.

Stimulants

If necessary, your GP or specialist may prescribe a type of medicine known as a stimulant, such as modafinil, dexamphetamine or methylphenidate.

These medications stimulate your central nervous system, which can help keep you awake during the day. They are usually taken as tablets every morning.

Common side effects of stimulants include:

• headaches
• nausea
• nervousness
• difficulty sleeping at night (insomnia)
• stomach aches
• irritability
• weight loss

Speak to your GP or specialist if you experience persistent or troublesome side effects while taking a stimulant. They may be able to prescribe an alternative medicine.

Modafinil in particular has also been linked to irregular heartbeats (arrhythmias) and increases in blood pressure, so you will need to be regularly monitored during treatment to check for these problems.

Sodium oxybate

Sodium oxybate is a medicine that can improve cataplexy and help you sleep at night, which can also reduce daytime sleepiness. However, it is not yet funded by the NHS in many areas.

Sodium oxybate is a drinkable solution that is taken in two doses at night – the first when you get into bed, and the second two-and-a-half to four hours later (you may need to use an alarm clock to ensure you take the medicine at the right times).

You will need to take sodium oxybate two to three hours after having a meal, because food can affect the amount of medication absorbed into your body.

While taking sodium oxybate, you should avoid drinking alcohol. You should also avoid activities that require mental alertness, such as driving or operating heavy machinery, until at least six hours after taking the medication.

Common side effects of sodium oxybate include:

• nausea
• dizziness
• headaches
• diarrhoea
• bedwetting
• vomiting
• weight loss
• blurred vision

You should tell your GP or specialist if you are taking sodium oxybate and experiencing persistent or troublesome side effects.

Antidepressants

Although there is some uncertainty about how effective they are in treating narcolepsy, daily antidepressant tablets or capsules are sometimes used to treat symptoms such as cataplexy, hallucinations and sleep paralysis.

Many different types of antidepressant medication have been used to treat people with narcolepsy, including:

• selective serotonin reuptake inhibitors (SSRIs), such as femoxetine, fluoxetine and citalopram
• serotonin-noradrenaline reuptake inhibitors (SNRIs), such as venlafaxine
• tricyclic antidepressants (TCAs), such as imipramine and clomipramine

These medications are thought to work by altering the levels of certain chemicals in your brain. 

The side effects you may experience will depend on the specific medication you are taking, but general side effects of antidepressants can include:

• feeling agitated, shaky or anxious
• feeling sick
• dry mouth
• slight blurring of vision
• constipation
• dizziness
• drowsiness
• problems sleeping (insomnia)
• sexual dysfunction, such as erectile dysfunction in men or difficulty achieving orgasm

Most side effects will improve within a few weeks. Speak to your GP or specialist if you are experiencing any side effects that are particularly troublesome or persistent.

You should not stop taking antidepressants suddenly, as you may experience unpleasant withdrawal effects. If you want to stop taking your medication, your GP will reduce your dose gradually over a few weeks.