Nightmares, Night Terrors & Sleep Paralysis: When Sleep Goes Wrong

What if the thing sitting on your chest in the middle of the night… wasn’t a demon?

For centuries, terrifying nighttime experiences were blamed on witches, demons, spirits, and creatures that supposedly climbed onto your chest and suffocated you. But what if these stories were actually attempts to explain something happening inside the sleeping brain?

In this episode of The Cadaver’s Lessons, we explore the strange world of nightmares, night terrors, and sleep paralysis—what they are, how they differ, and what happens physiologically when sleep and wakefulness collide.

We travel from ancient Sumerian and Greek beliefs to the medieval incubus, the Old Hag, Jinn, Kanashibari, and other cultural explanations for sleep paralysis. Then we follow the evolution of sleep science through the discovery of EEGs, REM sleep, and our modern understanding of parasomnias.

We’ll also break down:

• Why nightmares usually happen during REM sleep
• Why night terrors can look terrifying but are often forgotten by the person experiencing them
• How REM atonia can leave you awake but temporarily unable to move
• Why sleep deprivation, stress, shift work, and irregular sleep schedules can trigger sleep paralysis
• When these experiences become a medical disorder
• How nightmares are treated, including imagery rehearsal therapy
• Why you generally shouldn't try to wake someone during a night terror

And in our Ethics Autopsy, we ask some uncomfortable questions: What happens when a medical symptom becomes a moral judgment? And when medicine encounters a culturally specific explanation for a real physiological experience, should we correct the belief—or respect it?

Because maybe humanity hasn't stopped believing in demons.

Maybe we just gave them medical names.

Class is in session.

• Cox AM. J R Soc Med. 2015;6(7):2054270415598091.
• Vernon A. Demons or Nightmares? A History of Night Terrors. 2024.
• de Sá JFR, Mota-Rolim SA. Front Psychol. 2016;7:1294.
• Cleveland Clinic. Parasomnias. 2025.
• Faccini J, Del-Monte J. Front Psychiatry. 2024;15:1461495.
• Medscape. Parasomnias. Accessed September 6, 2026.
• Leung AKC, et al. Curr Pediatr Rev. 2020;16(3):176-182.
• Schulz H, Salzarulo P. J Clin Sleep Med. 2016;12(7):1041-1052.
• Silber MH. Sleep. 2024;47(1).
• Bhalerao V, et al. Cureus. 2024;16(7).
• Mythfolks. Sleep Paralysis Folklore. Accessed September 6, 2026.
• Wellcome Collection. Sleep Paralysis: A Brief History of Fear, Treatment and Artistic Creativity. 2016.
• Brown C. Smithsonian Magazine. 2003.
• Weir K. Monitor on Psychology. 2024;55(7).
• Medscape. Nightmare Disorder. Accessed September 6, 2026.
• Shumway KR, et al. StatPearls. StatPearls Publishing. 2026.
• Medscape. Sleep Paralysis. Accessed September 6, 2026.