hypersomnia

noun

hy·​per·​som·​nia ˌhī-pər-ˈsäm-nē-ə 

: a disorder of sleep that is characterized by prolonged nocturnal sleep periods which typically occur at least three times a week, by sleep that is not restorative or refreshing, and by the presence of excessive daytime sleepiness

Note: Hypersomnia may occur secondary to a medical condition (such as sleep apnea or depression) or the use of certain medications or may arise spontaneously from an unknown cause.

The International Classification of Sleep Disorders defines idiopathic hypersomnia as a disorder of excessive sleepiness that is associated with major sleep episodes, the cause of which is presumed to lie in the central nervous system.

—Sudhansu Chokroverty

also : excessive daytime sleepiness not associated with disturbed nocturnal sleep : hypersomnolence

Psychology Today reports that people who persistently fall asleep at their desks may be suffering from the dread hypersomnia …

—Curt Suplee

Examples of hypersomnia in a Sentence

Recent Examples on the Web

Conditions like depression or anxiety might present themselves in undersleeping (insomnia), or oversleeping (hypersomnia). —Rachel Hale, USA Today, 9 Aug. 2025

Sleep attacks and cataplexy are signs of narcolepsy, but not hypersomnia. —Mark Gurarie, Health, 3 May 2025

Difficulty falling or staying asleep (insomnia) and sleeping more than usual (hypersomnia) arise with depression, bipolar disorder, anxiety disorders, and PTSD, among others.15 10. —Mark Gurarie, Verywell Health, 27 Feb. 2025

Some treatable sleep disorders, such as hypersomnia, sleep apnea, and narcolepsy, also result in excessive daytime fatigue, even if someone slept plenty the night before. —Jamie Ducharme, TIME, 10 Oct. 2024

The drug also aims to treat idiopathic hypersomnia, or IH. —Pia Singh, CNBC, 20 Sep. 2024

Word History

First Known Use

1863, in the meaning defined above

Rhymes for hypersomnia

• insomnia

Medical Definition

hypersomnia

noun

hy·​per·​som·​nia -ˈsäm-nē-ə 

1

: sleep of excessive depth or duration

2

: a disorder of sleep that is characterized by prolonged nocturnal sleep periods which typically occur at least three times a week, by sleep that is not restorative or refreshing, and by the presence of excessive daytime sleepiness

The International Classification of Sleep Disorders defines idiopathic hypersomnia as a disorder of excessive sleepiness that is associated with major sleep episodes, the cause of which is presumed to lie in the central nervous system.

—Sudhansu Chokroverty

also : excessive daytime sleepiness not associated with disturbed nocturnal sleep : hypersomnolence