The fact that sleep paralysis so often involves being visited by an entity, which is often otherworldly in some way, reminds me of the experiences people can have when they take the psychedelic substance N,N-Dimethyltryptamine (DMT). DMT is a chemical that is endogenous to humans (we produce it in our own brains, but usually in such small quantities that it doesn’t usually produce hallucinations). In the 1990s, a researcher called Rick Strassman conducted a series of experiments with DMT, in which he injected willing participants with the substance to see what they would experience (Strassman, 2001). The results were astonishing: with a high dose, many of the participants experienced entities of spiritual or otherworldly types: elves, aliens, imps, and so forth. Some of the experiences were pleasant, the entities comforting or loving; some experiences were very unpleasant, the entities malevolent or unfriendly. These experiences felt so real that many people – including Strassman himself – concluded that in fact they were real, and that DMT simply enables us to see beings that exist “out there” that we just can’t normally see.
But whether DMT experiences are “real” or not is beside the point I want to make here. What I find curious is the similarities between DMT experiences and sleep paralysis experiences. Both are characterised by the feeling of a presence or an entity which is often otherworldly. Both people who experience sleep paralysis, and those who have taken DMT, often report that the experience feels so intensely real that it leads them to conclude that it is real. Both types of experiences can be very positive or very negative (although on the whole it would appear that sleep paralysis is more usually unpleasant than DMT experiences). Is it possible that during sleep paralysis endogenous DMT is involved? The idea that endogenous DMT may be involved in dreaming per se has been around for decades (Callaway, 1988), but not the idea that it may be particularly involved in sleep paralysis. “Waking up” and being paralysed is an intensely stressful experience, and there are claims that DMT is produced at times of intense stress, like the moment of death or during extremely intense physical exercise. Could sleep paralysis be stressful enough to release enough endogenous DMT to produce hallucinations? At the moment we have no way of answering this question, so this nothing but pure speculation. (But it’s fun to speculate.)
Callaway, J. C. (1988). A proposed mechanism for the visions of dream sleep. Medical Hypotheses, 26, 119-124.
Strassman, R. (2001). DMT: The Spirit Molecule. Vermont: Park Street Press.
 Although it’s worth remembering that most of our dreams feel “real” when experience them.