In 1374, hundreds of people along the River Rhine compulsively danced for days at a time, swept up in a terrifying mania of mass, compulsive, dancing. The hysteria spread through north-Eastern France and the Netherlands, lasting for months. Similar "dancing epidemics" broke out over the next two centuries. The new issue of The Psychologist features a scientific look at this incredibly strange kind of hysteria. From The Psychologist:
An important clue to the cause of these bizarre outbreaks lies in the fact that they appear to have involved dissociative trance, a condition involving (among other things) a dramatic loss of self-control. It is hard to imagine people dancing for several days, with bruised and bloodied feet, except in an altered state of consciousness. But we also have eyewitness evidence that they were not fully conscious. Onlookers spoke of the dancing maniacs of 1374 as wild, frenzied and seeing visions. One noted that while ‘they danced their minds were no longer clear’ and another spoke of how, having wearied themselves through dancing and jumping, they went ‘raging like beasts over the land’ (Backman, 1952). The hundreds of possessed nuns described in chronicles, legal records, theological texts or the archives of the Catholic Inquisition were equally subject to dissociative trance (Newman, 1998; Rosen, 1968). Some may have simulated the behaviour of the demoniac as a means of eliciting positive attention (Walker, 1981), but the detailed descriptions of astute and cautious inquisitors leave little doubt that most were genuinely entranced.
How might we explain these epidemics of dissociation? Ergot could have induced hallucinations and convulsions in nuns who ate bread made from contaminated flour, but it is highly unlikely that ergotism would cause remorseless bouts of dancing (Berger, 1931). Nor is there any evidence that what the victims of mass possession ate or drank made any difference. Rather, as explained below, there are very strong indications that fearful and depressed communities were unusually prone to epidemic possession. And given that there is a well-established link between psychological stress and dissociation, this correlation is immediately suggestive of mass psychogenic illness.