Sleep Deprivation vs. Short Sleep Syndrome

Short sleep and the lack of sleep are two different things

There are more than 100 different sleeping and waking disorders, and it is easy to confuse one for the other. Many of the conditions are characterized by sleep deprivation in which you are unable to sleep for more than a few hours per night or have regular sleep disruptions (such as night terrors or "starts").

Although many people define sleep deprivation as getting less than six hours of sleep per night, there are those who seem to thrive on as little as four to five hours of sleep.

It is not uncommon to call both of these conditions insomnia. While sleep deprivation may very well be caused by insomnia—defined as having trouble falling asleep or staying asleep—it can also be the result of other common and uncommon sleep disorders.

By contrast, needing fewer than six hours of sleep per night without consequence has nothing to do with insomnia. Rather, it is a condition classified by researchers as short sleep syndrome (SSS).

Woman watching TV in bed

Sleep Deprivation

Sleep disorders are a broad range of conditions in which the inability to sleep affects your health and well-being. The vast range of disorders can be broadly classified as:

All of these conditions can result in sleep deprivation and a cascade of symptoms that interfere with your ability to function normally, including:

  • Clumsiness
  • Depression
  • Difficulty learning
  • Fatigue
  • Forgetfulness
  • Increased carbohydrate cravings
  • Irritability
  • Lethargy
  • Loss of concentration
  • Loss of motivation
  • Moodiness
  • Reduced sex drive
  • Weight gain

Over time, chronic sleep deprivation can blunt your immune response, leading to infections. It may also alter insulin production, increasing your risk for type 2 diabetes, and elevate your blood pressure, upping your risk of heart disease.

Short Sleep Syndrome

In contrast to sleep deprivation, short sleep syndrome (SSS) is defined as needing fewer than six hours of sleep per night on an ongoing basis and still being able to function normally.

People with SSS perform well at work or school despite short periods of sleep and don’t feel the need to take naps or catch up on sleep on weekends.

The cause of short sleep syndrome is poorly understood. However, a 2014 study published in the journal Sleep strongly suggests that genetics play a key role.

According to the investigators, the mutation of the BHLHE41 gene was isolated in a dizygotic (non-identical) twin who only needed a few hours of sleep per night. The other twin without the mutation had almost identical amounts of rapid eye movement (REM) and non-rapid eye movement (NREM) sleep but required a full night's rest to function normally.

It is believed that mutations like this interfere with two independent processes that modulate sleep patterns (the circadian clock) and the drive for sleep (sleep homeostasis). Under normal circumstances, any interruption of these processes would be expressed in the cerebral cortex of the brain with symptoms of sleep deprivation.

For reasons unknown, specific mutations of the BHLHE41 genes (and other similar genes) circumvent this process while blocking the consequential response of the cerebral cortex. As a result, the internal clock that regulates sleep is shortened without any bearing on a person's physical or mental health.

A Word From Verywell

If you are not adversely affected by short sleep duration, you do not have insomnia and should not be worried. Awakening refreshed after a few hours of sleep is a sign of good health, not an illness.

If a sleep problem lasts for more than three weeks and affects your ability to work, take care of your children, or manage daily routines, call your doctor who may refer you to a sleep specialist.

Resist the temptation to self-diagnose and self-treat what you assume to be insomnia. In some cases, poor sleep patterns may be a sign of a serious medical condition requiring specific treatment and care.

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  1. Medic G, Wille M, Hemels ME. Short- and long-term health consequences of sleep disruption. Nat Sci Sleep. 2017;9:151-161. doi:10.2147/NSS.S134864

  2. Pellegrino R, Kavakli IH, Goel N, et al. A Novel BHLHE41 Variant is Associated with Short Sleep and Resistance to Sleep Deprivation in Humans. Sleep. 2014;37(8):1327-1336. doi:10.5665/sleep.3924