From the night hag to neuroscience: the history of sleep paralysis

Long before anyone measured brainwaves, people were waking up paralysed and terrified, and they needed a way to explain it. Almost every culture came up with a figure that visits sleepers in the night: something that sits, presses, or sits on the chest while the body refuses to move.

In Newfoundland, this figure is the 'Old Hag', giving the whole experience its old English name: being 'hag-ridden'. The word 'nightmare' itself comes from this tradition. The Germanic 'mare' was a spirit believed to sit on a sleeper's chest, producing bad dreams and a crushing, breathless feeling - a description that maps almost perfectly onto a modern sleep paralysis episode.

In Japan, the same experience is called Kanashibari, meaning 'bound in metal', capturing the sensation of being restrained by an invisible force. In Brazil, folklore tells of the Pisadeira, an old woman who steps on the chest of anyone who sleeps on a full stomach. In parts of Egypt, sleep paralysis has historically been attributed to jinn, spirits that attack a person during the night; a 2013 study comparing Denmark and Egypt found the experience itself was equally common in both countries, though its cultural interpretation differed sharply.

The link between these night-time visitations and real accusations of witchcraft is well documented. Historian Owen Davies, in a widely cited 2003 paper in the journal Folklore, traced how nightmare experiences and sleep paralysis contributed to witchcraft accusations in early modern Europe, since victims genuinely felt attacked by a malevolent presence while unable to move or cry out.

The modern turn came from folklorist David Hufford, whose 1982 book 'The Terror That Comes in the Night' compared accounts across cultures and argued that a consistent physiological experience underlies these very different legends. Twentieth-century EEG and REM sleep research then supplied the missing mechanism, showing that awareness can return before muscle atonia switches off. The old hag, the mare, Kanashibari and the jinn turned out to be the same story, told in different languages, about the same ordinary quirk of the sleeping brain.