Sleep is a natural process that takes place regularly and naturally. We spend a third of our lives sleeping, which may feel like a long time to spend in this seemingly mundane behaviour, but sleep is restorative. It enables us to function the next morning. However, frightening experiences during sleep may haunt us for the rest of the day or even for days and months. One of these experiences is known as Sleep Paralysis.
Sleep paralysis is a parasomnia, meaning a strange experience associated with sleep in a supine position, which can last for a few seconds to minutes. Its onset is in adolescence with a prevalence of about 30%. It usually takes place between rapid eye movement (REM) sleep and wakefulness. REM sleep is characterised by rapid eye movements while the body’s muscles and all voluntary movements are suspended (muscle atonia). Our brain during REM is very active as if we are processing information. We also dream a lot when we are in REM sleep which may explain why we are shutting down our ability to move.
Sleep paralysis often takes place upon waking (hypnopompic) which is usually right after we had a REM episode, although it may also take place while transitioning to sleep (hypnagogic). During sleep paralysis, our body is paralysed, so we are unable to move or speak, while we can still move our eyes and breathe. Although breathing continues during paralysis, there is a drop in overall oxygen intake by about 40% compared to wakefulness, so waking up during this time while our body is paralysed, and our chest is lacking sufficient oxygen may feel very awkward. Even though this alone can be a strange feeling, sleep paralysis may sometimes be accompanied by strange sensations, usually negative which make the person anxious, afraid or even terrified. These sensations are hallucinations which can be auditory, visual or a combination of the two. The person may have an out-of-body experience or see someone, an intruder, hovering on top of them while they sleep. However, the most widely reported frightening sensation associated with sleep paralysis is sensing the presence of evil and experiencing a heavy chest, difficulty breathing and fear of dying.
This reported experience of the oppressed chest is universal, as several cultures have folklore associated with it, usually interwoven with a sense of spirituality, such as the incubus in Latin and Christian tradition from the Middle Ages, which is a male demon seeking to have sexual activities with sleeping women, or pisadeira in Brazil, which is a woman with long fingernails like a witch that lurks on the roofs waiting to sit on the stomach of those asleep. In Inuit, uqumangirniq occurs because of malevolent shamans who find people vulnerable while they sleep, and similarly, in Japanese, kanashibari or feeling totally bound, is also thought to be the result of a malevolent spell by another person. The first reference to sleep paralysis is believed however to be by Hippocrates around 400BC as efialtes, which was subsequently linked to the horned and wild-natured god Pan, who would have sex with sleeping individuals.
Although sleep paralysis has been known in some form or other for centuries, it is a phenomenon which is still poorly understood. Overall, there is no difference in the prevalence of sleep paralysis between men and women however there seems to be a higher prevalence among university students and those with existing mental health conditions. Specifically, those with traumatic experiences such as childhood sexual abuse or war trauma are more likely to experience sleep paralysis compared to those without. Individuals with panic disorder and especially those suffering from post-traumatic stress disorder (PTSD) are at greater risk for more frequent sleep paralysis episodes. Stress and anxiety conditions such as social anxiety, as well as the person’s reaction to the sensation of sleep paralysis itself, can also be a precipitating factor, associated with greater negative sensations such as the hovering experience and the severity of the episode. Moreover, other sleep-related conditions such as insomnia, sleep apnoea, poor sleep quality or hypersomnolence have also been associated with a greater risk for sleep paralysis which may explain why students are more vulnerable, given the academic pressures and poor sleep habits.
Although existing mental health conditions render a person susceptible to sleep paralysis episodes, the presence of other mental health conditions can hinder attention by health professionals as sleep paralysis may be overlooked for the sake of the other ‘main’ condition. Also, sleep paralysis is a symptom of narcolepsy, a rare neurological condition associated with inappropriate and rapid transitions from wakefulness to sleep and cataplexy or muscle paralysis. However, more attention is gradually directed to those who experience sleep paralysis in the absence of narcolepsy, also known as ‘isolated sleep paralysis’ acknowledging it as a condition which requires attention in its own right.
So, even though sleep paralysis is generally a harmless human experience, for some it may be a significantly distressing one. Frequent episodes of frightening sleep paralysis can cause anxiety, exacerbate existing anxiety, or lead to sleep-associated anxiety. Good sleep hygiene and lifestyle choices, effective management of stress and existing mental health conditions can help reduce the frequency and the severity of the symptoms of this strange experience, so we can still experience it but not become distressed because of it.
Key Reference: Hefnawy MT, et al. Prevalence and Clinical Characteristics of Sleeping Paralysis: A Systematic Review and Meta-Analysis. Cureus. 2024 Jan 30;16(1):e53212. doi: 10.7759/cureus.53212.
Posted in sleep on Oct 01, 2024