The Science Behind Sleep Paralysis

Imagine waking up to a pressure on your chest, and seeing something or someone sitting on you. You desperately try to get up, but you are unable to move. You try wiggling your fingers, but to no avail. You start panicking, and you find it difficult to breathe. You try calling for someone, but no voice comes out. This is what it is like to experience sleep paralysis, and for some, this happens quite often.

According to a paper published by Esther Olunu et al, sleep paralysis (SP) is “a state associated with the inability to move that occurs when an individual is about sleeping or just waking.” It is believed that around 7.6% of the general population experiences an episode of SP at least once in their lifetime, according to a 2011 study (Sharpless, Barber), with higher rates among students and psychiatric patients, especially those with PTSD or panic disorder. 

Hundreds of years ago, SP was thought to be a visit by a paranormal, evil entity attempting to squeeze the life out of its victim, possibly because people who experience SP often claim they feel paralyzed, unable to speak, and overwhelmed by fear. Often times people describe seeing someone lying in bed with them but not being able to see them. A study published in the Sleep Medicine journal reports that 58% of 185 patients diagnosed with SP sensed some kind of presence in their room, usually a non-human entity. According to the American Sleep Association, sleep paralysis can cause people to feel a pressure on their chest, as if someone is sitting on their lungs, or to feel as if their body is moving against their intention. Although some people describe their experience as pleasant, describing a sensation of weightlessness, most patients with SP have a negative experience.  

Now, there is a scientific rationale for sleep paralysis. There are two types of sleep: (rapid eye movement) REM sleep and (non-rapid eye movement) NREM sleep. During REM sleep, our eyes move rapidly, even though our eyelids stay shut. We dream mostly during REM sleep, and because dreams often are an emotional experience for us, the brain makes us temporarily paralyzed. This paralysis, called postural atonia, is a result of suppression of skeletal muscle tone by two major regions in the brain: the pons and the ventromedial medulla. During SP, people wake up mentally while still in that REM paralysis state, which is why people with the condition describe symptoms of not being able to move or speak upon waking. The hallucinations involved with SP are due to activation of the amygdala during REM dreams. The amygdala is known to be related to decision making and reactions, particularly fear response, which is why many people may see an intruder or nonhuman entity during their episodes. 

There are several known risk factors for sleep paralysis. These include sleep deprivation or insomnia, irregular sleeping patterns, narcolepsy, a family history of sleep paralysis, and sleeping on your back. Other risk factors include substance abuse, a history of trauma, and poor physical health. Frequency and severity of episodes are linked to anxiety-like symptoms, as well as lack of sleep. 

There is no set treatment for sleep paralysis, though some patients with extremely debilitating symptoms may receive antidepressants. Sleep paralysis can be largely improved by getting regular exercise, avoiding big meals and avoiding alcohol consumption before bed, having a regular sleep cycle, and getting enough hours of sleep. So, for those of you with SP, hopefully you will be able to sleep a little better, knowing that there is no real night terror out to get you. 


Mary Yoshikawa