Excessive sleepiness is the defining characteristic of hypersomnia disorders, but there is much more to understand about the category than its main symptom. A sleep disorders advocate explains why distinguishing between primary and secondary hypersomnia is crucial to diagnosing and treating patients appropriately.

There are several different disorders of hypersomnia, all of which have the same primary symptom: excessive sleepiness. Such excessive sleepiness significantly impacts quality of life in these patients. Mundane tasks like cleaning, taking a shower, and going to the store for milk become monumental tasks that use all of their energy and push these patients to nap during the day. Patients may be unable to maintain employment due to hypersomnia.

It is important to understand that there are two prevalent types of disorders in this category: primary hypersomnia and secondary hypersomnia. Importantly, the causes and treatment options of each type are distinct.

Primary Versus Secondary Hypersomnia

Secondary hypersomnia is a symptom of another medical condition. The patient may have constant sleepiness in the acute stages of the disease process and later in the process the symptoms can change.1 Hypersomnia patients can have normal days and even experience insomnia at times. A vast array of medical conditions can cause secondary hypersomnia, including renal, hepatic, circulatory, endocrine, neurological, metabolic, psychological, and meningo-encephalitic disorders. Other causes include sleep disorders, particularly restless legs syndrome, periodic limb movements, insufficient sleep, apnea, and uncontrolled circadian rhythm disorders. If the primary disorder can be eliminated, then secondary hypersomnia goes away.

Actor Robin Williams had secondary hypersomnia due to his Parkinson’s diagnosis and depression. Williams slept up to 18 hours a day for months. Before his death, he had a hard time getting out of bed and suffered from loss of appetite.2 His story reminds us of what can happen if hypersomnia is overlooked and not treated. Whether patients have a physical or psychological disorder, the symptoms will get worse if the person’s secondary hypersomnia is not addressed.

By contrast, primary hypersomnia is diagnosed when there is no known cause for severe long-term excessive daytime sleepiness. Disorders such as idiopathic hypersomnia, Kleine-Levin syndrome (KLS), and menstrual-related hypersomnia fit into this category. These three types of primary hypersomnia are explained further in the section below. Primary and idiopathic hypersomnia are often used interchangeably, but they should not be. This improper usage can be especially confusing to people who aren’t familiar with the disorders.

Types of Primary Hypersomnia

Idiopathic hypersomnia is a clinical entity that has a small list of specific symptoms. The most important symptom is extreme daytime sleepiness that never ceases.3 Even though the patient’s nighttime sleep is virtually perfect, patients feel like they haven’t slept in days. Idiopathic hypersomnia patients often have deeper sleep than the average person and will sleep 10+ hours a day. They may enter stage 3 and 4 sleep more quickly than most people. REM is still within normal limits and there aren’t frequent awakenings. Many patients have what’s called “sleep drunkenness,” in which they are in an alternate stage of consciousness for up to 4 hours upon awakening. These patients are not quite awake and are in and out of stage 1 sleep. Patients can be irritable or violent, fall back to sleep repeatedly, walk into walls, slur their words, and generally act inebriated.4 Sleep drunkenness can happen when waking up from a nap as well. Patients can sleep anywhere from 10 to 21 hours a day every day for years. It’s possible to stay awake past the point of exhaustion, but eventually the patients succumb to the intense sleepiness.

Kleine-Levin syndrome is a recurring primary hypersomnia where patients have episodes of severe sleepiness in which they can sleep all day and only awake to eat or go to the bathroom. These patients can have clear triggers and usually know when an episode is coming and ending because their symptoms change. After the episode, they may have a period of insomnia and then go back to living a normal life until the next episode. Length of episodes can be anywhere from a few days to over a year.

KLS is a devastating disorder that differs from idiopathic hypersomnia in several key ways. Patients with KLS usually awake from an episode with little to no memory of the time that has passed, whereas patients with idiopathic hypersomnia wake up and might wonder what day it is but still know approximately what the date is. KLS symptoms can differ in males and females, but idiopathic hypersomnia is the same for both sexes. Patients with KLS have distinct polysomnography (PSG) results both in and out of episode, whereas idiopathic hypersomnia patients have consistent results. Patients who are diagnosed with KLS are often treated with lithium or other medications that don’t help other hypersomnia patients.5

Menstrual-related hypersomnia is diagnosed when excessive daytime sleepiness occurs preceding menstruation. Usually sleepiness occurs several days beforehand, but it can happen during or after menstruation as well. It’s thought that menstrual-related hypersomnia has to do with hormone levels, particularly progesterone and/or estrogen.6

Perspectives on Hypersomnia

Hypersomnia was extensively studied by Bedrich Roth from 1946 to 1980. At the time, Roth had the largest hypersomnia patient database in the world. It was Roth who discovered that idiopathic hypersomnia was a distinct clinical entity that was different from other disorders of hypersomnia.1 He noted that idiopathic hypersomnia was not a catch-all diagnosis for those who don’t have narcolepsy. Somehow that observation has been lost over the years.

Idiopathic hypersomnia is often compared to narcolepsy, but the disorders are markedly different. PSG studies show that narcolepsy patients quickly fall into REM sleep, whereas idiopathic hypersomnia patients can quickly fall into NREM sleep. Idiopathic hypersomnia patients have perfect nighttime sleep, and narcolepsy patients often have frequent awakenings and insomnia. People with narcolepsy tend to wake up from naps refreshed, whereas people with idiopathic hypersomnia still feel like they haven’t slept. Patients can have diagnoses of narcolepsy and hypersomnia but cannot have both idiopathic hypersomnia and narcolepsy.



All hypersomnia spectrum disorders need more research and better treatment options. These devastating disorders affect quality of life, not just for patients but their families as well. Many patients cannot work, and those who do struggle immensely. There are no FDA-approved treatments for hypersomnia, KLS, or idiopathic hypersomnia, which means that insurance companies can refuse to pay for treatment and dictate which medications patients have to take—even if those medications don’t work for the patient. Treatments for hypersomnia-related disorders focus mainly on stimulants, but one of the biggest issues with taking stimulants is the eventual tolerance that develops. Then patients either have to find new medications or take “medication holidays,” in which they stop taking the stimulants for a period of time to see if the medication will start working again. This requires taking time off work or school with no guarantee that the stimulant will work when restarted.

David Rye, MD, and Andrew Jenkins, PhD, from Emory Sleep Center have been researching an endogenous somnogen that is found in many hypersomnia patients’ spinal fluid. Their finding that flumazenil, a medication used to bring patients out of anesthesia, has provided promise of a potential treatment to the hypersomnia community. Flumazenil is currently in phase 3 of clinical trials.

Patients and providers alike are confused by the different disorders of hypersomnia. PSG and Multiple Sleep Latency Test (MSLT) studies can help diagnose these disorders, but that alone isn’t enough to distinguish between them. Because there are no quick diagnostic answers and very little research on the topic, patients have suffered. It has resulted in some of the leading sleep disorder researchers writing their own definitions or grouping all of the disorders of hypersomnia together. It has also led to research papers not separating idiopathic hypersomnia and hypersomnia. Hypersomnia patients truly are the forgotten patients in sleep medicine.

Kasha Oelke is a sleep advocate as well as an idiopathic hypersomnia and sighted non-24 patient. She runs the website www.hypersomnia.info.


1. Roth B, Broughton R. Narcolepsy and Hypersomnia. 2nd ed. Basel, Switzerland: S. Karger AG; 1980: XII:193-95, 209:213-17.
2. Dillon N, McShane L. Robin Williams spent final days in darkened bedroom as depression worsened; friend Rebecca Erwin Spencer found his body. New York Daily News. http://www.nydailynews.com/entertainment/robin-williams-friend-rebecca-erwin-spencer-found-body-suicide-article-1.1901705. August 13, 2014.
3. American Academy of Sleep Medicine. The International Classification of Sleep Disorders: Diagnostic & Coding Manual. 2nd ed. Westchester, Ill: American Academy of Sleep Medicine; 2005: XVIII:297.
4. Roth B, Nevsimalova S, Rechtschaffen A. Hypersomnia with “sleep drunkenness.” Arch Gen Psychiatry. 1972;26:456–62.
5. Arnulf  I, Zeitzer JM, File J, Farber N, Mignot E. Kleine-Levin syndrome: a systematic review of 186 cases in the literature. Brain. 2005;128(Pt 12):2763-76. Epub 2005 Oct 17. Review.
6. Dauvilliers Y, Buguet A. Hypersomnia. Dialogues Clin Neurosci. 2005;7(4):347–56.