Sleep paralysis is a well-known syndrome where, usually during the the transition into and out of sleep, the muscles of the body become paralysed, and in many cases terrifying hallucinations occur. But there has been little understanding so far of what might cause these scary events, and as such clinicians are not very well advised on how both recognize, and treat, sufferers.
Researchers involved in a new study have attempted to shed a bit more light on the subject, by conducting a systematic review of 42 previous published studies that have investigated variables “associated with both the frequency and intensity of sleep paralysis episodes”.
They found that, although many of the most obvious categories – such as age, gender, and ethnicity – showed little evidence of difference in frequency and intensity of sleep paralysis experiences, there were a few areas that seemed to be related. One of those areas was a history of trauma or stress:
A confirmed or unconfirmed history of childhood sexual abuse (CSA) was found to be significantly related to frequency of sleep paralysis episodes… The frequency and intensity of intruder and incubus hallucinations were significantly greater in both CSA groups as compared to those who did not report sexual abuse… Sleep paralysis prevalence was significantly higher in both CSA groups compared to a control group who reported not having experienced CSA.
Other experiences of threatening/traumatic events also appear to be related to sleep paralysis. In a sample of Hmong immigrants living in the USA, stressful experiences during the Vietnam war (e.g., “I was exposed to chemical warfare”, “I lost family, close relatives or friends”) were related to increased odds of experiencing sleep paralysis. General experiences with potentially traumatic events (such as assault, death of a loved one, disasters, etc.) were found to be related to sleep paralysis in terms of the occurrence of a traumatic event. Also a link was found between increasing numbers of traumatic events experienced and sleep paralysis. Relatedly, self-report levels of life-stress showed similar associations with sleep paralysis.
The survey also found some evidence of a hereditary link to likelihood of suffering sleep paralysis, a higher level of sleep paralysis in those with narcolepsy, and also a higher frequency and intensity of the experience in individuals with higher “imaginativeness” – a composite measure “that comprised scales of absorption, fantasy proneness, magical thinking, imagery vividness, paranormal and mystic beliefs, perceptual aberration, and unusual sensory experiences”. (Though it’s possible there might be some correlation between “higher imaginativeness” and being a victim of trauma or stress.)
The study finishes by offering some ‘practice points’ for clinicians in identifying and treating likely sufferers of sleep paralysis, as well as a research agenda for future studies to continue improving our understanding of the phenomenon. And, the researchers note, the review suggests a couple of areas where potential interventions could be targeted at helping sufferers: “As factors such as anxiety and stress appear to be linked with sleep paralysis, techniques aiming to reduce levels of these factors [such as cognitive behavioural therapy (CBT)] may also help in alleviating sleep paralysis episodes.”
For non-sufferers of sleep paralysis, you can get a real feel for how horrible it can be by checking out Rodney Ascher’s documentary The Nightmare, which is available on Netflix (trailer below):