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Hypersomnolence is a condition marked by excessive and chronic daytime and nighttime sleepiness. People who live with hypersomnolence do not enjoy restorative nighttime sleep, even though some sleep up to seven hours a night, and so they tend to nap throughout the day—at work, at meals, even at social events. The condition is akin to (and used synonymously with) the term "hypersomnia," though hypersomnia technically refers to excessive daytime fatigue only. The sense of sleepiness reported by those with hypersomnolence is not typically experienced as instant or overwhelming; however, the napping does not bring the individual restorative rest or relief. Hypersomnolence is often experienced among many people who suffer from depression, and is a diagnostic marker of that condition.


People living with hypersomnolence do not have trouble falling asleep but they may have difficulty waking; they may find it hard to move, or they may feel confused and irritable. It can take from minutes to as long as hours for the individual to awaken fully. Including naps, people with hypersomnolence can sleep as much as nine hours a day, all without feeling refreshed.

They may also experience sleep inertia, also known as “sleep drunkenness”—periods of im­paired performance or reduced attention after awakening from nighttime sleep or a nap. During these episodes, which can last from minutes up to multiple hours, a person appears awake, but suffers a decline in motor dexterity, temporary memory struggles, feelings of disorientation, and grogginess, and they may behave inappropriately as well.

For a clinical diagnosis of hypersomnolence disorder to be made, according to the DSM-5, a person must experience the following symptoms at least three times per week for at least three months:

  • Excessive sleepiness, despite getting at least seven hours of sleep per night.
  • Recurrent daytime naps or lapses into sleep during the same day. While these naps may last as long as an hour, they are typically not experienced as restorative and do not fully restore alertness.
  • Non-restorative nighttime sleep that lasts for more than seven hours.
  • Difficulty fully waking from a long sleep and feelings of confusion or disorientation that may last minutes or hours.
  • Increased sleep time — up to 14-to-18 hours per day.
  • Significant distress or impairment in daily functioning as a result of excessive sleep.

Hypersomnolence is considered mild if one has difficulty maintaining alertness one or two days a week; moderate if that difficulty occurs more than three days a week; and severe if the difficulty persists for five to seven days a week.

Living with hypersomnolence can leave an individual prone to a range of other mental-health and cognitive challenges including anxiety, irritability, low energy, restlessness, slow thinking or speech, a loss of appetite, difficulty with memory, hallucinations, and an inability to function well at work, at home, or in social situations. They may struggle to meet professional obligations or keep appointments, especially in the morning.

Are people with hypersomnolence prone to depression?

Yes. Many people with the disorder also experience symptoms that meet the criteria for a diagnosis of depressive disorder. The constant feelings of tiredness that come from living with hypersomnolence can add stress to one’s personal, professional, and/or social lives that can bring on depressive episodes. In other cases, because excessive sleepiness is a hallmark of depressive disorders, so the two conditions can manifest in tandem.  Those living with hypersomnolence may ieself-medicate with stimulants to such an extent that they develop a substance-abuse disorder.

Do people with hypersomnolence sleepwalk or suddenly fall asleep?

Not exactly, but people experiencing hypersomnolence may shift into a mode of “automatic” behavior—carrying out everyday activities with little recall; for example, driving for several miles without being aware of how far they’d gone. Also, while an individual may seem to fall asleep suddenly, those naps typically follow an extended period of sleepiness and are unlikely to occur during moments requiring sustained, focused attention like work meetings or social gatherings.

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Some people appear to have a genetic predisposition to hypersomnolence, as the condition sometimes runs in families, but many others may also be vulnerable. Symptoms of hypersomnolence can be caused by the presence of other sleep disorders such as narcolepsy, sleep apnea, or a dysfunction within the autonomic nervous system. Physical ailments, such as a tumor, head trauma, or injury to the central nervous system can lead to hypersomnolence, and about 10 percent of cases appear to be caused by viral infections including HIV, mononucleosis, or Guillain-Barré syndrome.

Certain prescription medications, or withdrawal from them, can cause hypersomnolence as well, as can drug or alcohol abuse.

While stress can lead to a temporary increase of symptoms of hypersomnolence, stress is not a cause of the condition on its own.

How prevalent is hypersomnolence?

About 1 percent of the population may experience symptoms of hypersomnolence, particularly prolonged bouts of sleep inertia upon waking. The disorder appears to be equally common in males and females, and first onset is typically between age 17 and 24, although hypersomnolence caused by injury or the presence of other conditions can emerge at any age. An individual typically experiences some level of hypersomnolence symptoms for several years before seeking medical advice and having the condition diagnosed.

What other medical conditions may lead to hypersomnolence?

People living with multiple sclerosis, encephalitis, epilepsy, Alzheimer's disease, Parkinson's disease, multiple system atrophy, or obesity may be more vulnerable to developing hypersomnolence. Depression and bipolar disorder can lead to symptoms as well; it’s estimated that more than 40 percent of adults with depression also experience bouts of hypersomnolence, women somewhat more often than men.


Someone experiencing persistent inability to fall asleep at night, or feeling perpetually tired during the day, should see their primary care physician for referral to a sleep specialist.

Hypersomnolence can be treated with medications including amphetamines, methylphenidate, or modafinil. Some clinicians may also prescribe clonidine, levodopa, bromocriptine, antidepressants, or monoamine oxidase inhibitors (MAOIs).

Lifestyle changes may help limit the onset of hypersomnolence—a better diet, for example, or avoiding social activities or nighttime work that delays one’s bedtime.

American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition
Textbook of Clinical Neurology. 3rd ed.
University of Maryland Medical Pages
Last updated: 05/12/2022