Desiree Lano
Henry Fuseli, John. The Nightmare. 1781. Detroit Institute of Arts, Detroit, Michigan.
What is Sleep Paralysis?
Sleep paralysis is a terrifying phenomenon in which the sufferer is unable to move during the onset of sleep or during awakening. Eye movement and breathing are still functional; however, one can experience frightening hallucinations, the feeling of something heavy on the chest, and/or false illusions of muscle movement. It is largely seen in narcolepsy, a neurological disorder defined by daytime drowsiness, abnormal sleeping patterns, and cataplexy (loss of muscle tone when experiencing intense emotions). When sleep paralysis occurs without the presence of narcolepsy, this is referred to as isolated sleep paralysis (ISP) (Denis et al., 2017) and has a lifetime prevalence of 30%-50% in healthy individuals (Mume & Ikem, 2009). Research on the relationship between psychiatric conditions and sleep paralysis is scant, but there is good evidence for several conditions, most notably post-traumatic stress disorder (PTSD) and anxiety disorders. This article will discuss these variables, with a main focus on a great article by Wróbel-Knybel et al., 2022.
Associated Psychiatric Conditions
Post-traumatic stress disorder (PTSD) and anxiety disorders are significantly associated with ISP (Wróbel-Knybel et al., 2022), with a particularly strong correlation with anxiety and panic disorders (Mume & Ikem, 2009). More severe disorders (i.e., mood and psychotic disorders) have weaker evidence; however, there still seems to be a relationship. One study found that while there was no difference in lifetime prevalence of ISP between patients with schizophrenia and healthy controls, the frequency of ISP episodes was significantly higher in those with schizophrenia (Park & Yang, 2002). Though there is correlational evidence for a number of psychiatric disorders, the most prevalent are PTSD and anxiety disorders.
PTSD
There is evidence to suggest that PTSD is the disorder most correlated with sleep paralysis. In a study done by Wro`bel-Knybel et al., it was found that a greater severity of symptoms in those with PTSD is correlated with at least one episode of SP in firefighters, as well as an increase in the amount of SP episodes in those with PTSD (Wro`bel-Knybel et al., 2021). However, this study fails to assess PTSD and SP in the general population, which would be useful for drawing larger conclusions. Further research should include healthy controls to compare results between the two groups.
Anxiety Disorders
Wro`bel-Knybel et al., 2021 have found a positive correlation between episodes of SP and perceived stress in the same sample of firefighters, as well as a correlation between SP and higher levels of anxiety as a personality trait. Another notable correlation with PTSD found by these authors is a tendency to worry (Wro`bel-Knybel et al., 2021). Additionally, Otto et al. (2006) found a 20% prevalence in a sample of outpatients receiving treatment for anxiety disorders with comorbid SP. According to the authors of this study, this may be explained by the common sleep disruptions experienced in those with anxiety disorders. Perhaps treating these sleep and anxiety disorders in patients successfully can lead to a reduction in SP episodes.
Conclusion
SP is a somewhat understudied phenomenon, particularly when it comes to its relationship to psychiatric disorders. Recent research has shown SP to correlate strongly with both PTSD and anxiety-related disorders; however, its relationship with more severe disorders does seem to be weaker. Overall, more studies should be carried out and subsequently replicated in order to build more on our current knowledge. Knowing common predispositions and variables associated with this frightening condition can be useful for clinicians to effectively assess risk in their patients and come up with better solutions.
References
Denis, D., French, C. C., & Gregory, A. M. (2018). A systematic review of variables associated with sleep paralysis. Sleep Medicine Reviews, 38(38), 141–157. https://doi.org/10.1016/j.smrv.2017.05.005
Mume, C. O., & Ikem, I. C. (2009). Sleep Paralysis and psychopathology. South African Journal of Psychiatry, 15(4), 4. https://doi.org/10.4102/sajpsychiatry.v15i4.185
Wróbel-Knybel, P., Flis, M., Rog, J., Jalal, B., Wołkowski, L., & Karakuła-Juchnowicz, H. (2022). Characteristics of Sleep Paralysis and Its Association with Anxiety Symptoms, Perceived Stress, PTSD, and Other Variables Related to Lifestyle in Selected High Stress Exposed Professions. International Journal of Environmental Research and Public Health, 19(13), 7821. https://doi.org/10.3390/ijerph19137821
Park, J.-H., & Yang, C.-K. (2002). Sleep Paralysis in Schizophrenia and Mood Disorder Sleep Paralysis in Schizophrenia and Mood Disorder. Sleep Medicine and Psychophysiology, 9(2), 115–121.
Wróbel-Knybel, P., Rog, J., Jalal, B., Szewczyk, P., & Karakuła-Juchnowicz, H. (2021). Sleep Paralysis among Professional Firefighters and a Possible Association with PTSD—Online Survey-Based Study. International Journal of Environmental Research and Public Health, 18(18), 9442. https://doi.org/10.3390/ijerph18189442
Otto, M. W., Simon, N. M., Powers, M., Hinton, D., Zalta, A. K., & Pollack, M. H. (2006). Rates of isolated sleep paralysis in outpatients with anxiety disorders. Journal of Anxiety Disorders, 20(5), 687–693. https://doi.org/10.1016/j.janxdis.2005.07.002
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