Narcolepsy and idiopathic hypersomnia (IH) both lead to daytime sleepiness, fatigue, and brain fog. Narcolepsy can involve muscle weakness and sleep paralysis, while IH may lead to non-refreshing sleep. More similarities and differences exist.

Type 1 narcolepsy and idiopathic hypersomnia (IH) are two conditions associated with excessive sleepiness. Both conditions lead to fatigue and daytime sleepiness. Falling asleep briefly is also possible in both.

The two types of narcolepsy are:

  • Type 1: narcolepsy with cataplexy
  • Type 2: narcolepsy without cataplexy

Cataplexy refers to muscles suddenly going limp or weak.

The symptoms of IH are similar to type 2 narcolepsy. In fact, the two conditions can only be distinguished through a multiple sleep latency test (MSLT).

Type 1 narcolepsy is what most people refer to when talking about narcolepsy, and that’s what we will focus on in this article.

Important differences exist between type 1 narcolepsy and IH. These relate to symptoms, causes, and treatment.

Continue reading to discover more about these two conditions, what causes them, and how they’re treated.

The table below provides a quick comparison of the symptoms of type 1 narcolepsy and idiopathic hypersomnia.

Type 1 narcolepsyIdiopathic hypersomnia
Excessive daytime sleepinessYesYes
Sleep attacksYesYes
Brain fogYesYes
Sleep paralysisYesSometimes
Walking up in the nightYesNo
Automatic behaviorYesYes
Refreshing napsYesNo
Sleep drunkennessYesYes

Narcolepsy and IH share three important symptoms:

  • Excessive daytime sleepiness: This can include feeling extremely tired during the day or an overwhelming need to sleep during the day.
  • Sleep attacks: During a sleep attack, an individual falls asleep without warning. A sleep attack can last several seconds or up to a few minutes.
  • Brain fog: Feeling tired all the time can lead to brain fog, which is characterized by problems with memory, attention, or concentration. You may also feel like your mind has gone blank.

While there are some similarities between the two conditions, there are also several differences. Let’s go into a little more detail about each condition and how they can present.

What is narcolepsy?

Narcolepsy is a chronic neurological disorder that affects the sleep-wake cycle, which is controlled by the brain. For someone with narcolepsy, the brain is unable to regulate this cycle, which leads to symptoms like excessive daytime sleepiness and sleep attacks.

Sleep has several cycles that are associated with different levels of brain activity. These include:

  • Non-rapid eye movement (NREM) sleep: When you fall asleep, you typically move through three stages of NREM sleep first.
  • Rapid eye movement (REM) sleep: After you’ve moved through the stages of NREM sleep, you enter REM sleep. During this time, you may dream for a few minutes to hours.

During the night, you typically cycle through NREM and REM sleep. However, in people with narcolepsy, these sleep cycles are disrupted. This means that an individual may experience more fragmented, restless sleep.

Other symptoms of narcolepsy can include:

  • Cataplexy: Cataplexy is a sudden loss of muscle control. Episodes of cataplexy can range in severity, from feeling weak to completely collapsing. People with narcolepsy and cataplexy have what’s now referred to as type 1 narcolepsy, while those without cataplexy have what’s referred to as type 2 narcolepsy. Episodes can last from seconds to minutes. They’re often brought on by:
    • being surprised or excited
    • feeling angry or afraid
    • laughing
  • Sleep paralysis: Sleep paralysis is a temporary loss of the ability to move or speak either before falling asleep or after waking up. While sleep paralysis isn’t harmful, it can be frightening when it happens.
  • Hallucinations: People with narcolepsy can experience intense, potentially frightening sounds or visions upon falling asleep or waking up. Often, a person may feel that someone else is in the room with them.
  • Waking up in the night: People with narcolepsy often have restless sleep and frequently wake up.
  • Automatic behavior: Automatic behavior is a task or activity that’s done without having any memory of performing it.

The symptoms of narcolepsy generally don’t get worse with age. In fact, in some individuals, they may improve slightly over time.

What is idiopathic hypersomnia?

Hypersomnia is when an individual experiences excessive daytime sleepiness. Narcolepsy is a potential cause of hypersomnia.

The term “idiopathic” refers to a condition without an identifiable cause. Therefore, people with IH have excessive daytime sleepiness without a known cause.

In addition to excessive daytime sleepiness and sleep attacks, other common symptoms of IH may include:

  • Long, non-refreshing sleep: People with IH can sleep or nap for a long time. However, they typically don’t feel refreshed upon waking.
  • Sleep drunkenness: People who experience sleep drunkenness have difficulty waking or have a strong urge to go back to sleep.

It’s also possible that people with idiopathic hypersomnia may experience sleep paralysis and hallucinations, similar to some people with narcolepsy. However, these symptoms are generally less prominent than the ones listed above.

Like narcolepsy, IH is a chronic condition. Symptoms often remain the same over time, although their severity can sometimes fluctuate. In 14–25% of people, symptoms can spontaneously disappear.


People with narcolepsy often lack a chemical called hypocretin, which is found in the brain. This chemical is important for wakefulness and sleep cycle regulation.

It’s believed that in some people with narcolepsy, the immune system attacks areas of the brain that produce hypocretin. This can lead to a deficiency in hypocretin, which affects an individual’s sleep-wake cycle.

However, a lack of hypocretin isn’t found in all instances of narcolepsy. In these cases, the cause is generally unclear.

Genetics is believed to play a role in narcolepsy. In fact, up to 10% of people with narcolepsy have a close relative with similar symptoms. Genetic markers associated with narcolepsy have also been identified.

Narcolepsy can also be caused by an injury, tumor, or health condition that affects areas of the brain involved with sleep. This is called secondary narcolepsy.

Idiopathic hypersomnia

The exact cause of IH is currently unknown. It may be due to the overproduction of a small molecule that enhances the activity of gamma aminobutyric acid (GABA) receptors in the brain associated with promoting restful sleep.

It’s also possible that genetics may contribute to the development of IH. About 34–38% of people with IH have a family member with hypersomnia or another sleep disorder.

Some examples of known causes of hypersomnia are:

The diagnostic process is similar for both narcolepsy and IH. This is because narcolepsy is a potential cause of hypersomnia.

If you see a doctor for excessive daytime sleepiness they’ll want to find out if it’s caused by narcolepsy or another health condition, such as IH or sleep apnea.

A diagnosis of either narcolepsy or IH begins with a healthcare professional reviewing your medical history and doing a physical exam. During your appointment, they’ll ask you about:

  • your symptoms and how long you’ve had them
  • whether anyone else in your family has experienced similar symptoms
  • if you have any underlying health conditions
  • any medications you’re taking

Your doctor can then order additional tests to help determine what may be causing your symptoms. Some of these can include:

Lab tests

Lab tests typically involve the analysis of a blood or urine sample. Your healthcare professional can use the results of these tests to help rule out other conditions that may be causing your symptoms.


During a polysomnogram, or PSG, your sleep is monitored for an entire night. This is typically done in a facility. During the test, various body functions are monitored using sensors and small electrodes placed on your body.

A PSG monitors:

Multiple sleep latency test

A multiple sleep latency test (MSLT), is typically done the day after a PSG. This test measures when you fall asleep and how quickly REM sleep occurs.

People with narcolepsy often fall asleep and enter REM sleep quickly. People with IH fall asleep quickly but don’t have the same REM patterns as people with narcolepsy.

Measuring hypocretin

Your levels of hypocretin can be measured using a sample of cerebrospinal fluid collected from a lumbar puncture. However, this is only performed in rare instances.

Genetic testing

A blood sample may be collected to look for genetic markers associated with narcolepsy.

The treatments for narcolepsy and IH can depend on several factors, including the severity of your symptoms, age, and overall health. Your doctor will work with you to develop an appropriate treatment plan, which may include:

Lifestyle changes

Your doctor may suggest making lifestyle changes that promote good sleep. Some examples include:

  • determining a bedtime routine and sticking to it
  • promoting a sleep environment that’s quiet, comfortable, and free of distractions
  • doing a relaxing activity before bed
  • avoiding caffeine, nicotine, or alcohol before bed
  • avoiding a large meal shortly before going to bed
  • getting regular exercise each day


There are medications approved to treat narcolepsy, but this isn’t the case for IH. In some cases, people with IH may take narcolepsy medications off-label to treat their condition. Examples include:

  • Stimulants: Taking a stimulant medication can help prevent feelings of excessive daytime sleepiness.
  • Antidepressants: Some types of antidepressants can help with muscle control in people with narcolepsy.
  • Sodium oxybate: Sodium oxybate is a strong sedative that’s taken twice each night. It can help reduce narcolepsy symptoms, including excessive daytime sleepiness and cataplexy.

Nap therapy

Nap therapy involves taking several short, regularly scheduled naps during the day. This may help manage excessive daytime sleepiness and prevent sleep attacks.

Typically, nap therapy isn’t effective for IH, as people with IH don’t tend to find naps restorative.

Safety counseling

People with narcolepsy and IH can often feel very tired or even fall asleep for brief periods. This can be dangerous for activities such as driving or operating heavy machinery.

Is hypersomnia the same as narcolepsy?

No. Idiopathic hypersomnia may be a symptom of narcolepsy, but they are different. Type 1 narcolepsy can manifest with cataplexy (sudden muscle weakness), while hypersomnia does not. Hypersomnia typically presents with interrupted and unrefreshing sleep, which isn’t typical in narcolepsy.

Sleep attacks and excessive daytime sleepiness are common to both idiopathic hypersomnia and narcolepsy.

Type 2 narcolepsy doesn’t present with cataplexy and it’s similar in symptoms to hypersomia. Only a specialized test can detect the difference.

Is hypersomnia part of ADHD?

Hypersomnia isn’t a symptom of attention deficit hyperactivity disorder (ADHD). However, some people with narcolepsy and hypersomnia may experience difficulty focusing and completing tasks. This may look similar to some symptoms of ADHD.

How do you know if you have idiopathic hypersomnia?

Symptoms of IH may include persistent fatigue and sleepiness, difficulty waking up, dizziness when waking up, and not feeling rested after a long sleep. These symptoms may have other causes, though. Only a healthcare professional can provide an accurate diagnosis.

Is hypersomnia a disability?

The Social Security Administration (SSA) does not include narcolepsy or hypersomnia in the list of covered disabilities. However, if you cannot work due to your symptoms, you may apply for disability benefits. You’ll need a medical report that explains your symptoms are persistent and severe enough to prevent you from working.

Make an appointment with a medical professional if you:

  • frequently feel extremely tired during the day
  • find yourself falling asleep briefly or napping often during the day
  • experience symptoms like sudden muscle weakness, sleep paralysis, or hallucinations
  • notice that your symptoms are having a significant effect on your daily life

A medical professional can work to determine if your symptoms are due to narcolepsy, IH, or another health condition. They can then recommend an appropriate treatment plan.

Type 1 narcolepsy and IH are similar conditions. In both narcolepsy and IH, an individual can experience symptoms like extreme daytime tiredness, sleep attacks, and brain fog.

Type 1 narcolepsy can have additional symptoms, including cataplexy, sleep paralysis, and hallucinations. People with IH can have additional symptoms, such as long, non-refreshing sleep and sleep drunkenness.

Narcolepsy is caused by a disruption to the brain’s sleep-wake cycle, often but not always due to low levels of a chemical called hypocretin. The exact cause of IH is still unknown.

Both conditions can be treated using lifestyle changes and medications. Nap therapy may also be effective for narcolepsy.

Be sure to see your doctor if you experience excessive daytime sleepiness that significantly affects your daily life.