These eerie -- and at times terrifying -- experiences are caused by a phenomenon known as sleep paralysis.
For centuries episodes of sleep paralysis have been attributed to supernatural forces, or believed to be the work of demons. But there’s a biological explanation for why we enter this bizarre state.
What Is Sleep Paralysis?
Sleep paralysis is classified as a parasomnia: A disorder that is characterized by undesired behavior that is brought on by sleep. As its name suggests, sleep paralysis causes you to be temporarily unable to move your body while you are conscious and aware of your surroundings.
This parasomnia happens during two distinct times in your sleep cycle:
- Hypnagogic or Predormital - While you’re first drifting off to sleep.
- Hypnopompic or Postdormital - When you’re waking up from sleep.
An episode of sleep paralysis usually resolves on its own, but being touched by someone, or spoken to may also cause you to snap out of it. Some people find that making an intense effort to move their body can end an episode.
Sleep paralysis is by no means a rare disorder. In fact, most people will experience sleep paralysis at least once or twice during their lifetime. The disorder typically makes its first appearance when you reach your teens, and occurs with the most frequency between the ages of 20-30 years.
While isolated incidents of sleep paralysis are by no means something to be overly concerned about, if you are experiencing multiple episodes on a regular basis they could have a negative impact on your health and the quality of your sleep. Sleep paralysis can also be a sign that you are suffering from narcolepsy.
Demons, Death & Hallucinations - Sleep Paralysis Is Not A New Phenomenon
Medical reports describing what is now known as sleep paralysis date back to 400 BCE -- uncovered in an ancient Chinese book about dreams. Personal stories about these terrifying experiences can be found throughout all of history and across all cultures, all sharing similar themes and imagery.
Historians describe this parasomnia’s pervasive influence on art: with perhaps the most notable illustration of this being 18th century painter Henry Fuseli’s “The Nightmare,” which depicts a sleeping woman with a demon sitting on her chest. A more recent example is the work of photographer Nicolas Bruno who, after suffering from episodes of sleep paralysis for over a decade, began to recreate his nightmares as a form of therapeutic release.
But art is not the only thing that has been shaped by this frightening disorder: Sleep paralysis is believed to be the true cause behind accounts of supernatural experiences. From demons, to modern day alien abductions, the symptoms of sleep paralysis appear to coincide perfectly with the variety of sensations described in these accounts.
What Does Sleep Paralysis Feel Like?
Every individual experiences sleep paralysis in a slightly different way, and the accompanying sensations can vary significantly in both their presentation and severity.
An episode can last anywhere from a few seconds to several minutes, during which you are unable to move your body or talk, while maintaining full awareness of what’s happening. Some people experience anxiety during an episode, especially if the paralysis is accompanied by hallucinations.
During an episode of sleep paralysis you may experience:
- Be unable to move: Paralysis is both the number one defining characteristic of this parasomnia and the first symptom you typically become aware of when experiencing an episode. Sometimes you may attribute your inability to move to being caused by some outside force.
- Have a clear perception of your surroundings: Most people report feeling fully alert and conscious during an episode. You’re able to clearly perceive your surroundings, and you feel firmly rooted in reality and not as if you are dreaming.
- Sense of anxiety, fear or dread: For some people, sleep paralysis brings on intense feelings of fear. This is often experienced as a gradual progression, with a sense of apprehension growing into terror. These emotional symptoms may even include feelings associated with death and dying.
- Feel as if someone is in the room: You may feel as if there is someone -- or something -- in the room with you. This “presence” can be either seen or simply perceived as a sensation of not being alone. People often attribute qualities of “evil” to this presence.
- Experience chest pressure and/or difficulty breathing: Although breathing is not physically obstructed, you may feel as if you are having difficulty catching your breath due to a physical weight being exerted on your chest. Sometimes this chest pressure is felt as if it is caused by an external force.
- Other bizarre sensations: Sleep paralysis may be accompanied by a variety of hallucinations that can affect any or all your senses. You may see, hear or smell things that are not actually present or experience different physical sensations such as hot and cold or as if you’re floating.
Some people believe that episodes of sleep paralysis are responsible for reports of alien abduction and paranormal experiences. Researchers have divided the hallucinations associated with sleep paralysis into three categories:
- The Intruder: An evil presence
- The Incubus: Something or someone pressing on your chest
- Levitation: The sensation of being lifted and moved from your bed
When combined, these types of hallucinations produce a terrifying experience that may be interpreted as an abduction or a haunting. Researchers at the University of Waterloo in Canada uncovered that people experience more distress following an episode of sleep paralysis if they hold supernatural beliefs. 
What Causes Sleep Paralysis?
For some people, knowing what mechanism is behind their unsettling symptoms can help mediate the fear and anxiety associated with them. Additionally, learning what is triggering your episodes of sleep paralysis enables you to form a strategy for prevention.
Sleep paralysis is caused by an error when your body is switching from one stage of sleep to another. Instead of smoothly transitioning, elements of the stage of sleep called REM (rapid eye movement) happen while you’re still awake.
REM is a very special stage of sleep, during which our brains are highly active and the majority of dreaming occurs. One characteristic of REM is that your body -- excluding your eyes and breathing muscles -- is paralyzed in order to prevent you from acting out your dreams.
This is why sleep paralysis occurs at those two distinct times of sleep: When falling asleep and when waking up. The paralysis portion of this stage of sleep is either happening too early or lingering on when we become conscious.
As for what causes REM-associated paralysis to pop up at the wrong times, there isn’t one simple answer. However, what all of these potential triggers have in common is that they affect the quality of your sleep and how your body regulates your sleep cycles.
Possible causes of sleep paralysis:
- Sleep Deprivation: Not getting enough sleep -- whether it’s due to insomnia or poor sleeping habits -- increases your likelihood of experiencing sleep paralysis.
- Changes in Sleeping Patterns: Undergoing a sudden change in your sleeping patterns, such as that caused by jet lag or working night shifts, also raises your risk.
- Narcolepsy: Sleep paralysis is considered to be one of the symptoms of narcolepsy -- a sleep disorder that impacts the onset of REM sleep.
- Other Sleep Disorders: Any sleep disturbance can bring on episodes of sleep paralysis. Additionally, studies have linked nighttime leg cramps with the parasomnia.
- Mental Health: From stress to bipolar disorder, your mental health is integral to the quality of your sleep.
- Sleeping On Your Back: The majority of sleep paralysis episodes happen when the sleeper in lying on their backs.
- Medications: Certain medications, such as those used to treat ADHD, have been shown to cause an increase in sleep paralysis.
- Substance Abuse: Drug and alcohol use, as well as withdrawal from these substances, often leads to sleep disturbances. In turn, this can increase the frequency of episodes of sleep paralysis.
- Genetics: You’re more likely to experience sleep paralysis if other members of your family do.
Anyone can experience sleep paralysis. The disorder affects both men and women equally, and can occur at any age. It’s estimated that up to 40% of people experience regular episodes of sleep paralysis; however, very frequent episodes only occur in 5% of people.
How Is Sleep Paralysis Diagnosed?
Determining whether or not what you’re experiencing is sleep paralysis is fairly straightforward and you can come to this conclusion on your own. Since this parasomnia does not pose any risk for your health most cases don’t require medical intervention.
However, if you answer yes to any of the following questions it’s a good idea to discuss your symptoms with your primary care provider:
- Do you experience sleep paralysis frequently?
- Have you developed anxiety about going to sleep?
- Are you having trouble getting sufficient sleep?
- Do you feel excessively sleepy during the day?
- Are you experiencing any other symptoms of narcolepsy?
The main goal of your appointment will be to rule out other sleep disorders (like narcolepsy) and to identify any other organic cause for your symptoms (such as medications or drug and alcohol consumption).
In order to do this your doctor will ask detailed questions about your symptoms: When they started, how long they last, and what sensations accompany the episodes.
Your doctor may ask you fill out a sleep diary for a few weeks in order to track the frequency and severity of your symptoms, as well as your general sleeping habits. This information not only helps to pinpoint the cause of your sleep paralysis, but can also help your doctor figure out how best to correct it.
Polysomnogram & Multiple Sleep Latency Test (MSLT)
If your doctor suspects a sleep disorder may be causing your symptoms, they may refer you to a sleep specialist for further testing. There are two tests typically used to examine your sleeping patterns:
- Polysomnogram: A polysomnogram is an overnight study that is either completed at home or in a specialized sleep lab. A variety of physiological measures are taken as you go to sleep for the right, including: heart rate, breathing, muscle tone and brain waves.
- Multiple Sleep Latency Test (MSLT): The MSLT helps provide an objective measure of your level of tiredness during the day. You’ll be asked to take four naps, during which a device will record how long it takes you to fall asleep and the stages of sleep you enter. This test is often used to diagnose narcolepsy.
How Can You Treat Sleep Paralysis?
Treatments for sleep paralysis are designed to tackle what is triggering your episodes. Your options range from implementing healthy lifestyle changes to taking medications that help regulate your sleep cycles.
For the majority of people that have only occasional sleep paralysis, practicing proper sleep hygiene can help reduce or eliminate your symptoms altogether. Sleep hygiene is simply a fancy word used to describe lifestyle habits that promote healthy sleep patterns.
Sleep Hygiene Tips For Sleep Paralysis:
- Get enough sleep: Adults need 7 to 8 hours of sleep every day in order to be well-rested. If you are unable to sleep enough at night, schedule some naps into your day to make up the lost time.
- Follow of sleep-wake schedule: Try to go to sleep and wake up at roughly the same time every day. Sticking to a set sleep-wake schedule keeps your circadian rhythms that control your sleep cycles in check.
- Change your sleep position: If you sleep on your back switching to your side can help reduce the chances that you’ll have an episode of sleep paralysis. Propping your body up with pillows, or sewing a tennis ball into the back of your pajama top can help ensure you’ll stay that way.
- Exercise regularly: Staying active during the day has been proven to promote healthier sleep patterns and is effective in treating a variety of sleep disorders.
- Reduce your stress: Stress has a negative impact on your central nervous system and the quality of your sleep. Include a relaxing activity in your bedtime routine -- such as taking a hot bath or meditating -- in order to prepare your body and mind for rest.
- Avoid caffeine and alcohol: Both caffeine and alcohol can wreak havoc on your sleep cycles. Don’t consume these substances too close to bedtime to prevent them from interfering with your sleep.
If your sleep paralysis is caused by an underlying condition or you have frequent intense episodes you should consult with your doctor for advice. Undergoing treatments for your other sleep disorders, mental health conditions, or switching medications may resolve your sleep paralysis.
When sleep paralysis is associated with narcolepsy, you may be prescribed an antidepressant medication. These drugs, such as clomipramine, are used to alter REM sleep and are typically prescribed at lower doses than those used to treat depression.
What Can You Do If You’re Having A Sleep Paralysis Episode?
Even with treatment you may still have occasional episodes of sleep paralysis. However, there are ways you can learn to better navigate the experience to make it less distressing.
Proponents of lucid dreaming believe that sleep paralysis can serve as a starting-point to this unique type of dream. A lucid dream is one in which you are consciously aware of what is happening, and you can choose how to interact with your surrounding or even manipulate the content of your dream.
Some people even train themselves to enter a state of sleep paralysis so that they can bring on a lucid dream.
The techniques used focus on relieving the stress and anxiety associated with the experience of sleep paralysis. 
- Repeat to yourself that you are in sleep paralysis, remind yourself that this is a benign state and you are in no real danger.
- Take deep, controlled breaths. This will help slow down your heart rate and demonstrate that you can breathe normally.
At this point, if you want to explore lucid dreaming you would introduce your intention and focus on where you’d like to go. We have an in-depth guide to lucid dreaming if you’re interesting in exploring it.