Sleep paralysis is a sleep disorder characterized by episodes of awakenings during sleep cycles when one cannot move any muscle, not even for opening the eyes or moving the mouth, feeling basically paralyzed. The experience can be pretty terrifying as the line between the dreaming state and reality fades away. For a better understanding of this condition, we need to explore the stages, physiological processes, and mechanisms of sleep.

Why is sleep so important?

Like eating and drinking water, sleeping is one of the vital physiological activities we must perform in order to live a healthy life.

In the past, scientists believed that during sleep the brain becomes dormant, now, modern science has proved that in fact, during sleep our brain engages in a lot of processes preparing us for the next day and at the same time filtering and processing the new information we acquired over the previous day.

To try and grasp the many activities our brains perform during one night’s sleep, scientists have had divided sleep into sleep cycles, each sleep cycle is composed of four stages of sleep.

While we sleep, a lot of physiological processes happen, with the help of these processes it’s been made easy to differentiate between Non-Rapid Eye Movement sleep (non-REM) and Rapid Eye Movement sleep (REM).

Mainly there are two types of sleep: non-REM sleep and REM sleep, that switch between one another throughout the night. We spend more time in non-REM sleep, as the first three stages of the sleep cycles are non-REM, with only the fourth being REM sleep. When one sleep cycle ends, another one begins, the only difference between sleep cycles throughout the night is the length of the sleep stages, which prolongs as the night progresses. One sleep cycle lasts about 90 to 110 minutes and we go through 4 to 6 sleep cycles per night.

During non-REM sleep our whole body relaxes, the brain’s activity slows down, and with it, the core temperature drops, the heart rate, blood pressure, and breathing rate slow down, and our muscles relax a little bit more with each stage of non-REM sleep until they become completely paralyzed in the deep sleep state (3rd non-REM stage) as this prepares us for entering the final stage of the sleep cycle, REM sleep. During REM sleep the brain becomes active again as if we were awake, but the muscles remain paralyzed preventing us from acting out our dreams, as the most vivid dreams occur during REM sleep. With the whole body immobilized, only our eyes move, behind the closed eyelids, hence the name Rapid Eye Movement. The heart rate and breathing rate increase during this stage to match the energy consumed while dreaming.

The 4 stages of sleep

The first three stages are non-REM sleep, also known as quiet sleep and the fourth and last one is the REM sleep stage, also called active sleep, paradoxically so.

Also, before entering the first non-REM sleep stage, there is a small period of time called entering sleep, during which you are still aware and alert, but feel like drifting off. In this period things like the impression of hearing someone call your name or the sensation that you’re falling can be experienced. Another common phenomenon while entering sleep is the myoclonic jerk, you know you have experienced this if you’ve ever jolted for no apparent reason, as you are trying to fall asleep.

1st non-REM stage:

• Lasts about 10 minutes and represents the transition from the wakefulness state to the sleep state;
• The most important physiological change that happens during this stage is that the brain slows down, and with it so do the heartbeat and the breathing rate, also the muscles relax as well, though twitching may occur.

2nd non-REM stage:

• Lasts about 20 minutes and during this stage, you become less aware of your surroundings;
• Physiological changes: body temperature drops, eye movements stop, the heartbeat and the breathing rate become regular;
• Beneficial effects: memory consolidation, meaning that the brain gathers, processes, and filters new memories from the previous day.

3rd non-REM stage (deep sleep):

• Lasts about one hour and during this stage of deep sleep any activity or noise coming from the environment usually fail to wake up the sleeping person;
• Physiological changes: muscles are now completely relaxed, the blood pressure drops and the breathing rate slows down once more;
• Beneficial effects: the body begins the reparative process, the term “reparative” has a broad sense, because the healing happens at the cellular, molecular and network levels;
• As the body is engaged in the physical repairs, the brain is involved in consolidating the declarative memories, this includes sorting through any facts, general knowledge, or personal experiences you had that day.

REM sleep (final stage):

• Lasts about 30 minutes and during this stage the whole body is immobilized, only the eyes move rapidly;
• Physiological changes: brain activity increases as if we were awake, the heart rate and breathing rate also increase and became irregular;
• Dreams happen in this stage;
• Beneficial effects: the brain has an enormous capacity of clearing out useless information and filtering and learning new information, also the emotional memory is consolidated during this stage.

What is Sleep paralysis?

As mentioned before, sleep paralysis is a state when one has the impression of waking up and not being able to move or speak. This is possible because the “waking up” part occurs during the dream state of sleep, more exactly, during the REM sleep stage, when the muscles are completely relaxed, thus giving the impression of being paralyzed.

Sleep paralysis – causes:

Sleep paralysis usually occurs during the REM sleep stage of the sleep cycle, when the muscles are completely paralyzed, the reason why we become aware during this stage is not completely known, but it is believed that other sleep disorders are involved. There are two mechanisms that help regulate our sleep: the circadian rhythm (sleep-wake cycles) and homeostasis (any process that helps maintain stable conditions for survival). Any disturbances involving these mechanisms increase the risk of sleep paralysis, for example, the circadian rhythm of shift workers, especially night shift workers, is deeply disturbed as these workers sleep during the day and are active during the night, the same thing happens, only to a smaller scale, with jet leg syndrome.

Other medical issues that favor the occurrence of sleep paralysis are sleep apnea, restless leg syndrome, and narcolepsy. On the other hand, sleep paralysis can be triggered by stress, lack of sleep, substance abuse, alcohol abuse, especially right before going to sleep, and certain medications like the drugs used to treat ADHD. Some psychiatric disorders can also be involved, such as bipolar disorder, general anxiety disorder, or post-traumatic stress disorder (PTSD).

The usual reason someone starts experiencing sleep paralysis episodes is sleep deprivation, either induced by other sleep disorders or by psychological stress experienced by the individual.

Types of sleep paralysis

Depending on the sleep stage of the sleep cycle in which sleep paralysis occurs, there can be two types of this condition:

• Hypnagogic (Predormital) sleep paralysis – it occurs during the first stages of sleep, as you are trying to fall asleep, it happens because your awareness doesn’t diminish as you’re falling asleep, letting you feel your body becoming more and more relaxed, inducing the “feeling paralyzed” mood;
• Hypnopompic (Postdormital) sleep paralysis – it occurs during REM sleep, as you are preparing for waking up, it happens because you become aware of your surroundings before your muscles can become active again, the result being you “feeling paralyzed”, not being able to move or speak.

Sleep paralysis – symptoms

The main, most frightening symptom of sleep paralysis is being awake, but not able to move or speak. This can be pretty terrifying as you don’t know if what’s happening is real or just a dream. As if it wasn’t enough, most people that have experienced the disorder, have declared that they were feeling as if there was a negative presence in the room with them, but more often than not, they could not identify the entity.

Sleep paralysis appears different from person to person, some say they feel like being suffocated by a faceless, shapeless entity, some say they see scary creatures or even aliens laying on their beds, others say they see a creepy old hag with claws in the corner of the room and for others, it’s just the feeling of being watched or in danger. Just like this the term “sleep paralysis demon” came to life, as it was the closest way for people to describe what they were feeling or rather to justify the evil presence they were sensing.

Of course, there is no evil entity involved, just our brain’s way to make sense of what we’re feeling during the sleep paralysis experience. The medical term for experiencing the sleep paralysis demon is called a hallucination, it can be hypnagogic if it occurs while falling asleep or hypnopompic if it happens while waking up.

Sleep paralysis vs Night terrors

Night terrors or nightmares usually occur during the 3rd stage of non-REM sleep, also called deep sleep, during this stage is difficult to be aroused. Nightmares typically occur early in the night, whereas sleep paralysis happens during the later sleep cycles of the night, around daybreak.

After both sleep paralysis and night terrors, you fall back asleep within minutes, of course, if the episode is not too traumatic, because if that’s the case you’re probably going to be fully awake and aware by the time you realize what was happening.

It can be pretty easy for the one experiencing these to tell them apart, as they are felt in unique ways, the most important difference between the two is that during nightmares you’re completely asleep and unaware, whereas with sleep paralysis you’re somewhat aware, but not fully awakened.

Also, it’s important to mention that these distinctive conditions appear at different stages in life, night terrors typically occur in children, and sleep paralysis is most common with adults.

How is sleep paralysis diagnosed?

The best way to confirm if you have this condition or not is by talking to a doctor. In the thorough medical history exam, your physician is going to ask a bunch of questions about your experiences during sleep paralysis and sleep schedule, followed by questions about other medical issues you and your family might have, all in order to put the proper diagnosis and start the best way of treatment.

Sometimes further examination is needed if the patient is too greatly affected and had developed anxiety about going to bed or increased sleepiness over the day. In these cases, a sleep specialist and a sleep clinic may be recommended to properly evaluate all your sleep disturbances.

Sleep paralysis – treatment

If sleep paralysis is not triggered by any underlying issues, like narcolepsy or mental disorders, there is no treatment needed, your doctor will recommend ways for you to improve your sleep, that involve changing a few habits around your bedtime, such habits can be:

• Adopting a different sleep position, if you’re usually sleeping on your back; it is proved that sleeping on your back can, in fact, trigger a sleep paralysis episode.
• Having a regular sleep schedule, going to be roughly at the same time each night and waking up around the same time each morning.
• Making sure you get the ideal amount of sleep hours each night; six to eight hours of sleep, depending on the individual’s needs.
• Exercising regularly, but not right before going to bed; it is recommended that at least 4 hours have passed since the physical activity, before going to bed.

Of course, there are some habits you would want to stop doing right before bed like:

• Eating a big, consistent meal;
• Drinking alcohol or caffeine;
• Smoking.

If your sleep paralysis is caused by a mental disorder, a psychiatrist must be consulted, as the medication needed to treat these disorders must be administrated accordingly to the patient’s needs. A class of meds that can be used are benzodiazepines, these drugs are addictive and must the taken with care and under the specialized supervision of a psychiatrist, to make sure the result you get is the result you want.

Therapy is always useful with this condition, no matter the cause of the occurrence, your doctor can refer you to a therapist specialized in cognitive behavioral therapy (CBT), as is the most effective, teaching the patient how to cope with overwhelming problems by breaking them down into smaller parts of the same issue.

Sleep paralysis – prevention

With no underlying condition, preventing sleep paralysis is pretty easy, all you need to do is to change the harmful sleep habits like eating, smoking, or drinking alcohol right before going to bed. Even something apparently not important, like your sleeping position, matters, so adjusting to a sleeping position facing down can do wonders, as studies have proved that sleeping on your back can trigger sleep paralysis.

Another thing that can help prevent sleep paralysis is setting the right mood for the bedroom, this implies cooling the room a bit before sleeping, the best temperature for a good night’s sleep is around 15.6 to 19.4 degrees Celsius. Something else you can do is to make sure there is no source of light to disrupt your sleep and avoid any source of blue light, like your phone, the TV, or your computer, before going to bed or in the bedroom.

Another simple thing you can do is to relax before bed, you can achieve this by taking a warm bath, reading a book, or engaging in any other activity you find soothing, also try not to lie in bed awake as this can lead to a certain kind of anxiety surrounding bedtime, on the long run, so go to bed when you already feel sleepy.

Conclusion

Sleep is one of the most important physiological processes that we need to perform every day to ensure our overall wellbeing. During sleep our brain is partaking in many activities that are getting us refreshed and ready for the next day, every single one of them is important for the proper functioning of the cerebral cortex. With every sleep stage, the brain engages in different activities, at first, it relaxes, recharges itself, then it clears out the waste, during the first stages of the sleep cycle, and as the night progresses, and the latter stages install, it’s becoming more active and it starts processing, filtering and learning the new information we gathered the previous day. It is believed that the real learning process happens during sleep, as it gives the brain time to assimilate and properly store information, either emotional or logical information, and just like this, new memories are embedded into our core memory. Aside from the beneficial effects on our memory and learning and concentrating skills, sleeping has a hugely beneficial impact on the healing process of our physical body, being able to repair tissues injured after a trauma, as well as being able to release a special kind of proteins called cytokines that fight inflammation and infections.

Your takeaway should be that a night of good 8-hour sleep is essential for the proper functioning of your entire body, not just your brain. Sleep deprivation and medical insomnia are bad for your memory and focus skills and if the conditions aggravate and become chronic, they can lead to serious diseases like high blood pressure and diabetes, and even heart attacks and cerebral strokes, they can also trigger sleep paralysis. On the other hand, too much sleep can also lead to other medical issues like heart diseases and diabetes. 

Sleep paralysis typically occurs in people who are sleep deprived either because of stress, a change in sleep schedule like working a night shift or changing time zones, or because of more serious medical conditions like insomnia, restless leg syndrome, sleep apnea, or psychiatric disorders.

The experience in itself is pretty terrifying and feeling paralyzed can be traumatic, especially if sleep paralysis occurs regularly. Aside from a “good scare”, one or two episodes do not represent much concern, more so, if they occurred at a time when the one experiencing them was overwhelmed by stress and the condition can resolve by changing a few habits before bedtime and making sure the sleep needs are met, no medication necessary. But if sleep paralysis occurs rather often, it can disturb the much-needed sleep process and at the same time, it can cause other medical and psychiatric issues, so a doctor must be consulted.