“Men, it has been well said, think in herds; it will be seen that they go mad in herds, while they only recover their senses slowly, and one by one.” Charles Mackay may have written those words in 1841 in his social science classic, Extraordinary Popular Delusions and the Madness of Crowds, but what he has to say about mass manias and the behavior of crowds remains absolutely relevant today—as anyone who’s ever gone to a midnight sale of one of the Twilight books could tell you.

Mob mentality also goes some of the way—but not all the way—in explaining these real manias and outbreaks of strange behavior that came on disturbingly fast and disappeared just as rapidly. (Please note, Bieber Fever is not on the list.)

1. The Deadly Dancing Mania of the Middle Ages

In 1374, dozens of villages along the Rhine River were in the grips of a deadly plague—a dancing plague called choreomania. By the hundreds, villagers took to the streets leaping, jerking, and hopping to music no one else could hear. They barely ate or slept, and just danced, sometimes for days on end, until their bloodied feet could support them no more.

The plague swept the countryside and, almost just as suddenly as it had come, disappeared. Until July 1518, in Strasbourg, when a woman called Frau Troffea picked up the tune again and danced for days on end. Within a week, she was joined by 34 people; by the end of the month, the crowd had swelled to 400. If they’d been inmates in a Philippine prison, the whole thing would have been choreographed, set to “Thriller” and uploaded to YouTube, but since this was the Middle Ages, they just died. Dozens perished, having literally danced themselves into heart attacks, strokes, and exhaustion. And, just as before, it just went away.

So what the hell happened? Historians, psychologists and scientists have tried to forensically get to the bottom of the dancing mystery. For a while, the prevailing theory was that it was a mass psychotic episode sparked by eating bread tainted by ergot, a mold that grows on the stalks of damp rye. When consumed, it can cause convulsions, shaking and delirium.

But John Waller, a history professor at Michigan State University, disagrees: According to all contemporary accounts of both outbreaks, the sufferers were dancing, not convulsing (in the mold’s defense, the two can be difficult to distinguish). And as to the other popular theory, that the victims were part of some heretic dancing cult, Waller says there’s nothing to suggest that they wanted to dance.

So Waller has a different theory—that these plagues were mass psychogenic illnesses, sparked by pious fear and depression. Both manias were preceded by periods of devastating famine, crop failures, dramatic floods, and all manner of Biblical catastrophe. Anxiety, fear, depression, and superstition—in particular, the belief that God was sending down plagues to persecute the guilty—made people susceptible to falling into this kind of involuntary trance state. And dancing plagues were the calling card of one St. Vitus, an early Christian martyr venerated with dance parties, meaning that the idea was already in the victims’ heads. All it took was one person to start it, and then everyone else followed.

Strasbourg wasn’t the last time a dancing plague ripped through a population—the most recent appears to be in the 1840s in Madagascar, where people danced as if possessed—but this epidemic appears to be rooted in a particular cultural milieu.

2. The Tanganyika Laughter Epidemic of 1962

It all started with a joke. But after 95 students at a girls’ boarding school in Tanganyika (now Tanzania) were stricken by the laughing plague, forcing the school to shut down for two months, it didn’t really seem funny anymore.

The laughing epidemic began on January 30th, 1962, at the mission-run girls’ school in a tiny rural village in the Bukoba region of Tanganyika, according to a 1963 report Central African Medical Journal. It started with a bout of uncontrollable laughing among three pupils, which turned into a crying jag attended by anxiety, the fear of being chased, and in some cases, violence when restrained. The these symptoms quickly spread through the school, apparently transmitted by contact with an infected person; onset was sudden, and could last anywhere from a few hours to 16 days.

The school was forced to shut down in March after more than half the students—95 out of 159—were affected. And then, 10 days after the closure, the disease popped up again, this time in a village 55 miles away. Several of the sick girls had come from the village and, though the medical journal isn’t clear on this point, had probably returned while the school was shuttered. In all, some 217 people were afflicted in April and May in that village. The disease then spread through the countryside; each time, the Typhoid Mary was a victim who had either been at the closed girls’ school or had come in contact with them.

But as in the cases of most psychogenic illness, there was nothing physically wrong with the afflicted. They exhibited no fevers or convulsions, and their blood work produced nothing interesting; theories that they were victims of some kind of psychotropic mold didn’t hold water when it was clear that they had no other symptoms. And, as the medical journal rather unkindly pointed out, “No literate and relatively sophisticated members of society have been attacked.”

3. Dromomania, or Pathological Tourism

Most people like to take a holiday now and again. Some people, however, just can’t stop. Dromomania refers to the uncontrollable urge to travel, a pathological tourism, and it was all the rage in France between 1886 and 1909. The man who exemplified dromomania for the European medical establishment was a gas-fitter from Bordeaux, one Jean-Albert Dadas. Dadas was admitted to the Saint-Andre Hospital in Bordeaux in 1886, after he had just returned from a truly epic journey. He was exhausted, of course, but also confused, vague and foggy—he couldn’t remember where he’d been and what he’d done.

A doctor at the hospital managed to piece together his story and submit it to a medical journal under the charming name, Les aliénés voyageurs, or The Mad Travellers. Dadas’ compulsive traveling allegedly began after he illegally parted company with the French army near Mons in 1881. From there, he went east to Prague, then Berlin, through what was then East Prussia, finally to Moscow. In Moscow, he was arrested—a czar had just been assassinated and Dadas had the misfortune of being mistaken for a member of the nihilist movement responsible—and forced to march back to exile in Turkey. This may have actually suited his particular mental illness just fine. In Constantinople, he was somehow rescued by the French consulate and put on the road to Vienna, where he again took up work as a gas-fitter.

Dadas’ story inspired several other cases of dromomania in France at the time. And if it wasn’t an actual epidemic, in the sense that a large number of people were actually suffering from it, there seemed to be an epidemic about talking about it amongst medical circles. It seemed to die out by around 1909, right around the time the “alienists” (proto-psychologists) started to actively investigate it.

Dadas’ adventure also seemed to take place at a time when the medical community, some driven by pseudo sciences like eugenics, were interested in parsing out all manner of mental illness into discrete manias. Dadas could have also been dealing with a bit of drapetomania, an obsession with running away from home, though he was definitely not suffering from clinomania, a refusal to leave one’s bed. Of course, his dromomania probably would have been much easier on him if he’d also been suffering from cartacoethes, the compulsion to see maps everywhere.

4. Koro, or Genital Retraction Syndrome

Another “culture-bound syndrome,” koro refers to the irrational fear that one’s genitalia is shrinking or retracting into one’s body. And people have suffered it, usually in mass hysteria epidemics, since around 300 BCE. It’s particularly prevalent in Africa and Asia and is usually attended by severe anxiety (unsurprisingly) and fear of impending death, or loss of sexual ability. One of the most recent outbreaks of koro or, as it’s called in Western medical circles, Genital Retraction Syndrome, was in 1967 in Singapore, when more than 1000 men tried to stave off shrinkage using clamps and pegs.

Women have also been victims of the panic, often manifesting the fear that their breasts or nipples are disappearing. However, koro is more likely to strike men and, according to psychologists, more likely to strike men in societies where their worth is determined by their reproductive ability. Psychologists usually blame cultural circumstance, pointing out that epidemics tend to follow periods of social tension or widespread anxiety; Chinese medicine, however, blamed female fox spirits, while in Africa, it was usually considered the result of witchcraft.

5. Motor Hysteria

The Middle Ages were kind of boring, and probably even worse for the sometimes unwilling inhabitants of nunneries. So mewling like cats was one way to pass the time. Historical reports indicate that nunneries were rife with “motor hysteria,” a kind of mass psychogenic illness that had some women exhibiting the signs of demonic possession, others acting out in sexually disturbing ways, and one convent mewling like cats and trying to claw their way up trees.

The period of nuns behaving badly lasted around 300 years, beginning at around 1400, and affected convents across Europe. One of the last was perhaps the most deadly—in 1749, a woman at a convent in Wurzburg, Germany was beheaded on suspicion of being a witch after an episode of mass fainting, foaming at the mouth, and screaming. Usually, however, these episodes ended in someone calling in a priest for some exorcisms.

Waller, he of the investigations into the dancing plagues, also came up with a theory as to what would drive these nuns to distraction: A combination of stress and strong religious tradition of trance and possession.

Women who were sent to nunneries did not always go willingly, and convents, especially starting in the 1400s, were very harsh places. The rigorous devotion to spiritual betterment wasn’t for everyone and the stress and privations these women experienced could sometimes cause them to act out. When they would, it was often with behavior that stereotypically mimicked demonic possession: “They believed implicitly in the possibility of possession and so made themselves susceptible to it,” wrote Waller.