Hypersomnia is an amalgamation of two words – ‘hyper’ meaning too much and ‘somnia’ meaning sleep – that describes the condition of sleeping in excessive amounts or experiencing excessive sleepiness in the day. It’s not uncommon for hypersomnia (also called hypersomnolence) sufferers to experience both symptoms. 

There are some classification systems in which hypersomnia is referenced as specific disease entities such as idiopathic hypersomnia and similar sleep disorders while hypersomnolence refers to excessive daytime sleepiness or excessive sleeping regardless of the cause. 

A closer look at hypersomnolence (hyperinsomnia)

Hypersomnolence is a complicated trait, and its study is still relatively new compared to the many other disorders and medical symptoms that researchers know about. Still, the socioeconomic burden of it is huge. Current information shows that each hypersomnia disorder is categorized in three ways:

  • clinical symptoms
  • underlying biological cause
  • diagnostic testing.

The most common classification system for hypersomnia disorders is called International Classification of Sleep Disorders (ICSD). The third edition of it lays out a general category of central disorders of hypersomnolence. The category includes various disorders that cause excessive daytime sleepiness due to the central nervous system (brain). They share a common daytime sleepiness symptom. 

For this diagnosis to be properly made people must meet these criteria: their sleepiness cannot be caused by nighttime sleep problems (such as sleep apnea) or with the circadian rhythm. 

The third edition of ICSD lays out eight kinds of central hypersomnolence disorders:

  • Hypersomnia (as a result of a medical condition)
  • Hypersomnia (because of medication or other substance)
  • Hypersomnia (because of a psychiatric condition) 
  • Idiopathic hypersomnia
  • Insufficient sleep syndrome
  • Kleine-Levin syndrome
  • Narcolepsy type 1 (with cataplexy)
  • Narcolepsy type 2.

Primary or secondary: further breakdown of hypersomnia disorders

While the ICSD-3 doesn’t break the eight disorders down into further categories, they can be broken down into two classifications:

  • primary – occur on their own without another condition being the cause
  • secondary – occur because of another condition (either because of it or related to it)

The primary types of hypersomnia

The disorders that fall under this category include the Kleine-Levin Syndrome, idiopathic hypersomnia, and both types of narcolepsy – NT1 and NT2. 

The classification of these disorders is based mostly on two things – sleep testing results and symptoms. All four disorders entail excessive sleepiness.  Sleepiness in the Kleine-Levin syndrome is episodic – it can last days to weeks and then stop for months before occurring again. Patients will typically sleep for long periods of time, which will affect their thinking, personalities, and behavior. 

In the other three disorders people experience chronic excessive sleepiness without periods free from it. 

People who have narcolepsy type 1 also have cataplexy, which is a sudden onset of weakness as a result of a powerful emotion such as anger or humor. This condition doesn’t occur with many other conditions, which makes diagnosing someone with type 1 narcolepsy fairly easy. 

Diagnosis of three central hypersomnolence disorders is made with the Multiple Sleep Latency Test (daytime nap test). In the three disorders – both types of narcolepsy and idiopathic hypersomnia – people can easily fall asleep (in less than eight minutes on average). However, in narcolepsy, REM sleep takes place in at lest two naps. With idiopathic hypersomnia, REM occurs once or not at all. Idiopathic hypersomnia sufferers may also sleep for long periods of time with at least 11 hours of sleep in a 24-hour period. 

There have been cases where patients with narcolepsy type 2 slept for long periods, but the symptom didn’t meet the diagnostic criteria.  There are other clinical aspects – instances of paralysis upon waking up – which may be noted in some disorders, but have been seen in any of the three mentioned above and that’s why they are not considered in the primary diagnostic guidelines. 

People who have CDH may experience symptoms that relate to NT1, NT2, and IH, but how common they are is dependent on the disease. Since many symptoms happen with multiple disorders, a majority of them are not included in the official diagnostic criteria for each one. And not every patient with a particular diagnosis will experience this pattern of symptoms. 

How to categorize primary hypersomnias by underlying causes 

As you see, some primary hypersomnia syndromes have coinciding clinical aspects because the principal cause was not known before the diagnosis was made.  In this case a doctor may suggest doing a lumbar puncture (spinal tap) to collect and analyze cerebrospinal fluid. If there are low levels of hypocretin, it confirms type 1 narcolepsy diagnosis due to an autoimmune condition that is attacking the hypocretin-making nerve cells in the brain’s hypothalamus. 

Patients with idiopathic hypersomnia or type 2 narcolepsy have normal hypocretin levels. 


Doctors will use two tools to test for hypersomnia and to distinguish if a person has idiopathic hypersomnia or narcolepsy. They are:

  • overnight polysomnogram
  • Multiple Sleep Latency Test (MSLT).

The overnight polysomnogram involves an array of electrodes that will monitor the heart rate, brain waves, breathing patterns, oximetry, and legs muscle activity during sleep. If the results of this test are negative, it means that no diagnosable sleep-related breathing disorder can be found. After that doctors will conduct the MSLT.

In this test a sleep technologist will monitor just the heart rate and brain waves and will look at the data from the different sleep stages. The patient has five opportunities to sleep throughout the day at two-hour intervals, beginning at two hours following light on from the polysomnogram (which occurs at night). Each opportunity is 20 minutes long, but less than 20 if doctors observe measurable sleep.

The sleep technologist will record the test start time, the onset of sleep, and whether sleep progressed into REM sleep. Sleep physicians get a good idea of what the diagnosis is based on periods of REM sleep during the MSLT. Doctors may also ask patients to keep a detailed sleep journal and provide complete medical history. 

Treatment of primary hypersomnia disorders

The treatment that a person is recommended is based on their hypersomnia disorder. Narcolepsy patients have three classes of drugs that can be used: sodium oxybate, stimulants, and nonstimulants. Stimulant medications such as Ritalin and Adderall and nonstimulant medications such as Armodafinil and Modafinil may be used. 

Nonstimulants are considered as such because they don’t have the same chemical makeups as stimulants do even though they help to keep people awake and alert. 

Sodium oxybate helps to relax the body so that it can go into deep sleep while improving daytime sleepiness. 

Other prescribed medications include monoamine oxidase inhibitors (MAOIs) and antidepressants. How do MAOIs work? They stop serotonin from breaking down, which is important for wakefulness. Medications for certain diseases related to hypersomnia such as muscular dystrophy and Parkinson’s disease are often used to treat the symptoms. 

For people with obstructive sleep apnea a CPAP (continuous positive airway pressure), BiPAP (bilevel positive airway pressure), and ASV device (adaptive servo-ventilation) may help to reduce the effects associated with excessive daytime sleepiness. 

Doctors may also suggest other changes in one’s behavior such as avoiding taking medications or stimulants that cause wakefulness or implementing a good sleep routine such as cool room, no noise or light, etc. Cognitive behavioral therapy can help to alleviate some of the symptoms as well. 

But like with any medical condition, it’s important to work with a physician to find the right therapies to treat your condition. In the long run your health will thank you for it. 

The secondary types of hypersomnia

Hypersomnia due to medical condition – the disorder is the result of some neuromuscular disorder such as myotonic dystrophy, a neurodegenerative disorder (Parkinson’s disease, Alzheimer’s disease, etc.), or a head injury. 

Hypersomnia because of medication or substance – the disorder is the result of a prescription or nonprescription medication or drug. 

Hypersomnia due to psychiatric disorder – the sleepiness in a patient with psychiatric disorders is not always caused by the psychiatric disorder. For instance, a person who is depressed and has hypersomnia must have both conditions and the two must be related. However, researchers do not know if depression causes hypersomnia or vice versa. 

Insufficient sleep syndrome – this is when a person regularly does not sleep enough hours per night. While each person varies in how much sleep they need, adults typically need between seven and nine hours a night.