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Idiopathic Hypersomnia

Medically Reviewed by Dr. Shelby Harris

Written by Jocelyn Zakri MPH, RRT, RPSGT, RST

What is Idiopathic Hypersomnia?

Idiopathic hypersomnia (IH) is one of 8 disorders classified as a central disorder of hypersomnolence and can be further categorized as a primary hypersomnia. Primary hypersomnias do not have other conditions associated with them – excessive sleepiness occurs independent of other medical conditions or medications.

Idiopathic hypersomnia causes excessive daytime sleepiness. Excessive daytime sleepiness or EDS, is a severe and extreme sleepiness that causes people to have difficulty maintaining wakefulness when they should be alert.

Despite getting adequate quantities of sleep, those with idiopathic hypersomnia remain sleepy and feel sleep deprived. The continuous threat of severe drowsiness or sleep can create dangerous situations not only to those experiencing EDS, but also to those in the immediate vicinity – especially if driving or use of machinery is necessary.

Symptoms of Idiopathic Hypersomnia Include:

There are several common symptoms found with idiopathic hypersomnia. The most notable is excessive daytime sleepiness. A majority of those with IH sleep between 10-12 hours per 24 hour period and remain sleepy.

Other symptoms include non-restorative sleep and sleep inertia. Upon waking, those with IH do not feel refreshed as one would normally feel after a long sleeping period. Sleep inertia refers to the period just after waking. Many with IH have significant difficulty with the sleep-to-wake transition and experience a longer period of post sleep grogginess.

What Causes Idiopathic Hypersomnia?

There is no known cause for idiopathic hypersomnia. Some research suggests that there may be a small molecule within the brain that interacts with the neurotransmitter responsible for promoting sleep.

Though little is known about this particular molecule, it is believed that if it is over produced, the effect is similar to that of medications used for sedation. Further research is necessary on how the mystery molecule interacts specifically, but it is thought to be a key component behind idiopathic hypersomnia.


Due to the lack of direct origin, there is no specific diagnostic tool that can be utilized in trying to diagnose idiopathic hypersomnia. Most physicians combine several components together as a means to determine which hypersomnolence disorder a person may be experiencing.

Diagnosis based on exclusion can be useful for many. Physicians may start by eliminating probable causes of excessive sleepiness, such as certain medications, other underlying disorders, disease states, or insufficient sleep.

Sleep diaries are particularly important as they can provide detailed sleep habits and patterns. Detailed medical histories and exams are also important tools used in diagnosis of IH.

Finally, an overnight polysomnogram followed by a daytime test known as the Multiple Sleep Latency Test or MSLT can aid in determining any underlying sleep disordered breathing as a cause for excessive sleepiness.

Together the compilation of information gathered along with the presence of EDS for a minimum of a three-month time period, can provide a clearer picture for proper diagnosis and treatment of idiopathic hypersomnia.


There is no cure for idiopathic hypersomnia. Treatment for idiopathic hypersomnia is similar to that for those with narcolepsy due to a similar symptom list and characteristics.

Usually, the first line of treatment includes the use of medications. Stimulants and non-stimulant wake promoting medications are utilized the most.

Stimulants include medications such as dextroamphetamine and methylphenidate. Non-stimulant medications include modafinil, solriamfetol and the newest member of the drug class, pitolisant.

In addition to medications, the use of cognitive behavioral therapy or CBT may also be beneficial to those with idiopathic hypersomnia.

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