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Sleep Paralysis

What is sleep paralysis and its consequences

According to data from Hospital Albert Einstein, in São Paulo, no less than two million people in Brazil suffer from a sleep disorder known as sleep paralysis. This disorder, which has no cure, can be really frightening because of its effects, which are characterized by the temporary inability to move and the possibility of suffering hallucinations in the transition from sleep to wakefulness, or vice versa.

In Brazil around 1% of our population is affected by it, in England this percentage is much more significant, and can reach 6% of the population, according to official statistics. But what is sleep paralysis, and what are its consequences? How does it happen, what explains it, and when should we seek specialized medical treatment? We asked our experts to answer some of the most common questions so that you know everything about sleep paralysis. Happy reading!

What is sleep paralysis?

Sleep paralysis is a sleep disorder that can happen to anyone, and is characterized by an episode during the transition between sleep and wakefulness, when the affected person is temporarily unable to move or speak. The person is in a state of temporary disconnection, with discontinuity of motor, perceptual, emotional or cognitive functions.

When affected by sleep paralysis, the person is almost asleep or waking up, but suddenly simply cannot perform a voluntary movement or say anything. In general, they may experience chest pain, such as momentary pressure, and may experience hallucinations.

Many people who have had an episode of sleep paralysis report that they felt like they were having a nightmare, but awake. It is important to note that this sleep disorder can be quite traumatic, and most of the time it is even frightening.

In general, an episode of sleep paralysis can last around two minutes, on average, but can be as long as ten minutes in some cases.

Classification of sleep paralysis episodes

The paralysis and hallucinations typical of sleep paralysis are really frightening, often creating an aura of terror for the affected person. These episodes are classified into three different types. Are they:

• Intruder: causes fear and the feeling that there is a stranger in the room. Affected people report the sensation of an evil presence, with visual and auditory hallucinations as well. Because of this, there are a number of myths that try to explain sleep paralysis – which have nothing to do with reality.

• Unusual Body Experience: It is also a common type, and it is classified by the sensation of floating. People affected by it report the feeling of leaving their body and seeing it in bed, as if above it. There is often an illusion of movement.

• Incubus: This is the mildest type, characterized by a feeling of pressure in the chest and shortness of breath. But it’s also quite frightening, and many people report that they believed they were experiencing a cardiac episode rather than an episode of sleep paralysis.

Sleep Paralysis Effects

It is very common for people affected by sleep paralysis to experience acute anxiety and even fear of sleep. The main effects of sleep paralysis are:

• Decrease in sleep quality

• Insomnia

• Tiredness

• Daytime sleepiness

• Lack of concentration and memory

• Worsening in school or work performance

• Demotivation

• Isolation and even removal from the social group

How can sleep paralysis be explained?

Sleep paralysis is a very common disorder, but it is still poorly studied, and its causes have not been fully clarified by scientists. It is believed that the lack of synchrony between changes in brain activity and muscle atony in the REM phase of sleep (Rapid Eye Movement – the phase where dreams happen) is responsible for the temporary paralysis that we experience throughout an episode of this sleep disorder.

Scientists are investigating associations of sleep paralysis with substance use, stress and trauma, genetic influences, anomalous beliefs, sleep problems and disorders, and psychiatric disorders. British studies indicate that post-traumatic stress disorder appears to be the most common risk factor, followed by panic disorder.

Why does sleep paralysis happen?

In Brazil, popular belief tries to explain the phenomena. The disturbance would be nothing more than a consequence of the action of “Velha Pisadeira”, an ancient Brazilian myth about a grumpy old witch, with a horrible appearance, who would live on the roofs of houses, ready to attack her victims in their sleep.

“Velha Pisadeira” would attack the person who eats too much before sleeping, stepping on their chest and leaving them momentarily breathless. What’s more, the victim is fully aware when attacked, but can’t move a single finger to defend themselves against the old woman. This is a very common urban legend, especially in the states of Minas Geais and São Paulo, and many people believe that this is the explanation for sleep paralysis. There are other myths, including ones involving abductions and extraterrestrials.

Beliefs aside, science explains this sleep disorder. What actually happens is that our voluntary muscle movements are inhibited from going from sleep to wakefulness, or vice versa. During the sleep paralysis episode, however, our eye and breathing movements are not altered and, therefore, our perception of the environment is clear and immediate.

Science also seeks to understand how the possible hallucinations caused by the disorder happen. Neurological studies associate hallucinations with an abrupt movement in and out of the REM sleep phase. Dreams and hallucinations are formed by vivid visual events and are extremely emotional. At this stage, the body remains paralyzed, with the exception, of course, of vital organs and also the genitals.

Experts point out that the disorder may be closely related to diseases such as narcolepsy (excessive sleepiness), high blood pressure, depression and anxiety. Sleeping face down is also pointed out as a possible cause. Periods of intense stress and sleep deprivation can also contribute to the occurrence of sleep paralysis episodes.

Other Possible Causes for Sleep Paralysis Episodes

• Irregular sleep;

• Constant sleep deprivation;

• Sudden changes in someone’s environment or life;

• A lucid dream that precedes the episode;

• Sleep induced by specific medications;

• Extreme tiredness;

• Bipolar disorder;

• Night cramps;

• Excessive drug use; • Excessive consumption of alcoholic beverages.

Who can be affected by sleep paralysis

In the literature on the subject, there is no relation between sleep paralysis and age and sex, although some individual studies point to a higher prevalence in women. In fact, absolutely anyone can experience an episode or more of sleep paralysis, including young children.

Researchers at the University of Pennsylvania, in the United States, carried out an extensive study on no less than 35 works by recognized scientists on the subject, published in scientific journals in the last 50 years, with the participation of a total of 36,533 people. Of this total, 20% claimed to have had at least one episode of sleep paralysis.

According to the study by scientists at the University of Pennsylvania, entitled “Sleep Medicine Reviews”, among psychiatric patients interviewed, 32% responded that they had already had at least one episode of the disorder, and among psychiatry students this percentage was 28%, both well above the previous 20%. The researchers then concluded that sleep paralysis may be more common among patients and students of psychiatry.

The treatment for sleep paralysis

Sleep paralysis can indeed be a frightening sleep disorder, but experts say there is nothing to worry about in the face of occasional episodes. After a few minutes after full awakening, everything is back to normal, with no sequelae.

Experts consider it a disease that requires treatment when it recurs. It was established that it must be amenable to medical treatment when there are at least two episodes within a period of six months or when it is associated with a strong emotional charge. Thus, those who have more frequent episodes of sleep paralysis and end up being afraid to go to sleep need to see a specialist.

Of course, it is important to understand the real cause for the patient to have episodes of sleep paralysis. The treating physician will investigate illnesses associated with this sleep disorder and may, for example, prescribe specific medications to decrease the REM sleep phase, for example. Psychotherapy sessions may be recommended for cases of high anxiety or depression, including the possibility of using medication prescribed by a psychiatrist.

Relation between sleep paralysis and sleep apnea

Sleep apnea is a sleep disorder that affects no less than 69% of the Brazilian population, according to data from the Instituto do Sono, in São Paulo. Known as obstructive sleep apnea (OSA), it causes a brief interruption during sleep, and this can be repeated even hundreds of times in the same night.

Experts say that those who have obstructive sleep apnea are more likely to develop an episode of sleep paralysis. This can happen because sleep habits and physiological functions are basically the same, they can be disrupted and this can affect the time to go to sleep.

Your doctor may request an actigraphy

Longitudinal follow-up of patients suffering from sleep paralysis is necessary to obtain answers to possible causes of symptoms. Actigraphy is one way of monitoring the patient, and is greatly requested by physicians who care for patients with sleep disorders, including sleep paralysis. It is performed using the actigraph, a device that looks a lot like a wristwatch.

Actigraphy, also known as actimetry, aims to follow the cycles of activity and rest, capturing, compiling and processing information relevant to the study of the rhythm of sleep and wakefulness. The actigraph is a state-of-the-art technology that provides all the support for the assistant physician’s research, and the most modern models also have temperature and light sensors, among others, offering an even deeper analysis.

The patient should wear the actigraph attached to the wrist of their non-dominant arm. That is, a patient who is right-handed must use it on the left arm, and vice versa. During its use, the device collects and compiles all the patient’s movements using accelerometers. At the end of the exam, the attending physician has extremely relevant information, which will help to establish the diagnosis and the best treatment for him.

The actigraph detects sleep and circadian rhythm disturbances, assesses the quality of sleep, the time a person spends in bed and sleep episodes throughout the day. It is a non-invasive test, absolutely painless and is highly requested by sleep doctors, psychiatrists, occupational physicians, behavioral psychologists and other professionals who study sleep disorders and circadian rhythm.


An episode of sleep paralysis is not a disease, but a symptom. This disorder should only be treated as a disease if it happens systematically, at least twice every six months. The doctor will seek to discover the cause in order to treat it.

Sleep doctors, neurologists and psychiatrists are the most indicated to assist people affected by this disorder. The simple report of the affected person is enough to classify the disorder. An actigraphy may be requested for a deeper and more analytical study of the patient’s sleep.

Doctors guarantee that sleep paralysis does not cause any harm to physical health, but it can have negative consequences, such as anxiety and even depression. Thus, a doctor should be sought if the episodes are repeated and provoke, for example, fear of falling asleep.



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