5 Reasons Why You Only Sleep a Few Hours a Night

There are more than 100 different sleeping and waking disorders, and it is easy to confuse them. Sleep deprivation often occurs with sleeping disorders.

If you cannot sleep for more than four to five hours per night (or less), you may have sleep deprivation. In addition, regular sleep interruptions from things like night terrors or "sleep starts" can also lead to sleep deprivation.

If you have trouble falling asleep or staying asleep, your sleep deprivation may be caused by insomnia. But it can also be caused by other sleep disorders.

For example, if you need fewer than six hours of sleep every night and don't have sleep deprivation symptoms, you likely do not have insomnia. Instead, you may have a condition known as short sleep syndrome (SSS).

This article explains the difference between sleep deprivation and SSS.

Sleep Deprivation

Being unable to sleep can affect your health and well-being. Sleep disorders fall under the following categories:

• Insomnia: Difficulty falling asleep or staying asleep
• Hypersomnia: Excessive daytime sleepiness caused by narcolepsy, obstructive sleep apnea, and other medical conditions
• Circadian rhythm disorders: When your biological clock is out of sync, such as in jet lag, irregular sleep-wake syndrome, and shift work syndrome
• Parasomnias: Behaviors that interrupt your sleep, such as sleep terrors, sleepwalking, and REM sleep behavior disorder

All of these conditions can cause sleep deprivation. Often, they affect your ability to function normally as you go through your day. Symptoms of sleep deprivation include:

• Clumsiness
• Depression
• Difficulty learning
• Drowsiness
• Fatigue
• Forgetfulness
• Increased carbohydrate cravings
• Irritability
• Less interest in sex
• Loss of motivation
• Moodiness
• Trouble concentrating
• Weight gain

Short Sleep Syndrome

Unlike sleep deprivation, people with short sleep syndrome (SSS) regularly need fewer than six hours of sleep per night and can still function normally.

People with SSS perform well at work or school even though they have short periods of sleep. They don’t feel the need to take naps or catch up on sleep on weekends.

The cause of short sleep syndrome is not well understood. However, a 2014 study published in the journal Sleep strongly suggests that genetics play a key role.

SSS and Gene Mutations

In one study, two non-identical twins got almost identical amounts of rapid eye movement (REM) and non-rapid eye movement (NREM) sleep. One twin had a mutation of the BHLHE41 gene and needed a few hours of sleep per night. The other didn't have the mutation and required a full night's rest to function normally.

It is thought that gene changes like this interfere with a person's sleep patterns and their drive for sleep. Usually, these kinds of sleep interferences would cause symptoms of sleep deprivation. But in people with certain gene mutations, it doesn't.

For some reason, specific changes to certain genes alter the way the brain responds to a lack of sleep. As a result, the internal clock that controls sleep is shortened without harming a person's physical or mental health.

Summary

Sleep deprivation can be caused by many different sleep disorders, including insomnia. It can cause symptoms that affect your ability to function throughout the day. For example, if you have sleep deprivation, you may have trouble concentrating, feel tired all of the time, or be crabby.

People with SSS, on the other hand, need less sleep. They do not experience negative symptoms as a result. In addition, research has found certain gene mutations in people with SSS.

A Word From Verywell

If you are not adversely affected by short sleep duration, you don't have insomnia and shouldn't be worried. Waking up refreshed after a few hours of sleep is a sign of good health, not an illness.

However, call your healthcare provider 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. They may refer you to a sleep specialist.

Don't try 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.