Sleep Paralysis: Night-mares, Nocebos and the Mind-Body Connection

"One of the most common hallucinatory experiences that people can have occurs around the boundaries of sleep, what we call hypnagogia. And the state in particular that can induce this is sleep paralysis, when you wake up but your muscles are still paralysed. There’s something about this state that seems to produce a range of hallucinatory phenomena, including feelings of presence, something I’ve written about in my book, Presence: The Strange Science and True Stories of the Unknown Other . These presences often seem to be very malevolent, and we have accounts of them from across cultures, all around the world, almost every society has its own name for this evil presence that comes at night. The case that Shelley Adler writes about is very striking. It relates to a spate of overnight deaths among young Hmong immigrants in the 1980s that seemed to be in response to a visitation from an evil spirit they called the tsog tsuam . This spirit would visit people if they’d done something wrong and needed to appease their elders in some way. The story of the young men’s deaths is really a demonstration of how powerful our expectations can be and how powerful cultural influences can be on both the experience of hallucination and the knock-on effects. As Adler describes it, the tsog tsuam would usually visit men in the family and if this happened at home the man—usually the father or leading man in the family—would visit a shaman to talk about what needs to be done to appease the elders. If they didn’t do that, they believed the tsog tsuam would come back and things will get worse. But, crucially, immigrant families who had fled the Vietnam War couldn’t visit the shaman. So, these transplanted communities, away from their usual cultural frames and under the stress of being refugees, have these unusual experiences, and don’t have their usual way of managing them, and things spiral from there. There’s still a debate around whether such ideas could be powerful enough to cause someone’s heart to stop. But the more we learn about the interaction between our bodily experiences and our perception of the world, the more we realise they are very interconnected. Experiments have shown that our judgements about what we perceive are closely linked to how we are feeling inside. If I were to show you a disgusted face— very quickly so you weren’t aware you had seen it—your heart rate would change, ever so slightly. That in turn changes how confident you are about your senses. So, in an unusual situation, you might be more likely to see things that aren’t there. How we are feeling inside can change what we think we are seeing, hearing, or sensing. Yes, ‘presence’ is a word people land on when ‘voice’ or ‘vision’ doesn’t quite cut it. I came across the idea through my work at Durham’s ‘ Hearing the Voice ‘ research project, where we regularly talk to people who hear voices, and more than one of the interviewees would say, ‘you know, it’s not just about sound.’ You can have the experience of an entity or a person who is close by, who is not making a sound but you just feel them. When you think about presences they pose a challenge: there’s this paradox of how do you perceive something you can’t see or hear or touch, it’s just something you seem to feel in your bones. But by calling it presence, you can see that people experience felt presences in a panoply of examples across different contexts, whether it’s due to dementia, or Parkinson’s, or grief and bereavement. One of the more profound examples is in survival situations and the phenomenon of Shackleton’s ‘ third man ‘: the fact that all three members of Ernest Shackleton’s Antarctic rescue mission reported an uncanny feeling during their perilous trek that they were four men, not three. The evidence from neurology and case studies of people who have damaged their brain suggests that presences could be caused by changing the body’s expectation of where it is in space, changes to our usual cues of proprioception—but the jury is out on that, and it only applies to some cases, such as perhaps sleep paralysis."