When Netflix dropped the thriller Bird Box in 2018, audiences were left wondering about the unseen monster that drove people to suicide. One popular theory points to mass hysterical contagion—now known as mass psychogenic illness (MPI)—where a single case spreads like a psychological wildfire. Below, we count down 10 disturbing cases of MPI that shocked communities, illustrating how fear, media, and social pressure can turn ordinary moments into collective nightmares.
10 Disturbing Cases of Mass Hysteria
10 The Twitching Teenagers
In October 2011, Thera Sanchez, the cheerleading captain at Le Roy Junior/Senior High School near Buffalo, New York, awoke from a nap only to discover she was uncontrollably twitching and jerking. Two weeks later, senior Lydia Parker began humming and swinging her arms erratically. What started as a duo soon ballooned to about 20 students—mostly teenage girls—exhibiting similar involuntary movements.
Parents grew frantic, suspecting the school’s water or playing fields were contaminated. Yet leading environmental experts found no evidence of any toxin that could cause such symptoms.
Dr. Laszlo Mechtler, who treated 15 of the affected teens at the Dent Neurologic Institute, noted that social media and press attention amplified the outbreak. He explained, “One thing we’ve learned is how social media and mainstream media can worsen the symptoms. The mass hysteria was really fueled by the national media, social media—all this promoted the worsening of symptoms by putting these people at the national forefront.” By the end of the term, most of the girls had returned to normal.
9 June Bug
In June 1962, a South Carolina dress‑making mill saw 62 workers develop nausea, dizziness, and a rash that seemed to “break out over the body.” The staff blamed a recent fabric shipment, believing insect bites were to blame.
Investigations by the U.S. Public Health Service uncovered no credible evidence of an insect vector. Instead, they concluded that the harsh working conditions of the era—combined with the stress of long hours—had created a fertile ground for a psychosomatic spread. The term “June Bug” likely emerged from an early, untrained medical team unfamiliar with such symptom clusters.
This episode exemplifies a social contagion, where tightly knit groups—here, mostly women supporting families—share stress‑induced symptoms that echo each other.
8 Tarantism
From the 15th to the 17th century in Italy, tarantism described a bizarre hysteria linked to alleged tarantula bites. Victims—convinced they’d been stung—experienced heightened excitability and restlessness, often breaking into frenetic dancing believed to be a cure.
In 1693, a Naples physician deliberately allowed two tarantula bites to test the theory. In front of six witnesses, he displayed no physical changes, debunking the notion that the spider’s venom caused the symptoms.
The phenomenon gave birth to the tarantella, a rapid, flirtatious couple’s dance. Renowned composers such as Frédéric Chopin, Franz Liszt, and Carl Maria von Weber all penned tarantella pieces, immortalizing the feverish rhythm of the era.
7 Tanganyika Laughter Epidemic
In 1962, Tanganyika (now Tanzania) experienced a contagious laughter outbreak that began at a girls’ school and quickly spread to neighboring villages. Over 1,000 individuals suffered bouts of uncontrollable giggling that lasted weeks, accompanied by hysterical crying, aimless running, and violent outbursts lasting from a few hours to more than two weeks. Fourteen schools were forced to close.
Researchers believe a single schoolgirl, anxious and prone to laughter, triggered the chain reaction. Christian Hempelmann observed, “We build up some magical psychic pressure, and laughter lets us release it. Statistically in this case, this did not release anything. These people were suffering, expressing their suffering through that. Nothing got better because they laughed.”
6 False Anthrax Alarms
On October 5, 2001, a letter that tested positive for anthrax claimed the life of the Sun newspaper’s picture editor, Bob Stevens, sending shockwaves worldwide. The anthrax antibiotic Cipro surged in sales, and an airplane in Dallas was forced to land when carpet crumbs were mistaken for anthrax spores. In England, both Canterbury Cathedral and the London Stock Exchange were evacuated over false alarms.
During that month, four letters tested positive for anthrax, yet more than 3,000 cases turned out to be hoaxes or false alarms. Media outlets saw a massive spike in sales as the public craved information, prompting criticism that journalists were hyping the threat. Steve Caprus, executive producer of NBC Nightly News, urged reporters to “deal with facts—not hyping or being overly dramatic.” Over subsequent months, five people died from inhaling anthrax, and 17 others were infected.
5 St. John’s Dance
In 1374, the streets of Aachen, Germany, were seized by an inexplicable dancing mania, later dubbed “St. John’s Dance.” Sufferers formed circles, hand‑in‑hand, dancing wildly for hours on end until exhaustion forced them to collapse. They reported extreme oppression and groaning as if in agony, only to recover after being tightly swathed around the waist.
Justus Friedrich Karl Hecker chronicled the phenomenon in his 1888 work The Black Death and The Dancing Mania, describing the relentless, delirious choreography that baffled observers for centuries.
4 Elsa Perea Flores School
In the summer of 2016, the Elsa Perea Flores School in Tarapoto, Peru, fell prey to a mass hysteria episode that afflicted nearly 100 children aged 11‑14. Students reported terrifying visions of a tall, bearded man dressed in black who seemed intent on strangling them, accompanied by seizures, fainting, muscular convulsions, delirium, and repeated screaming.
One pupil recounted, “It’s disturbing for me to think about it. It’s as if someone kept on chasing me from behind. It was a tall man all dressed in black and with a big beard and it felt like he was trying to strangle me.” Another added, “Several children from different classrooms fainted at the same time. I got nauseous and started vomiting. I heard voices. A man in black chased me and wanted to touch me.” Locals attributed the outbreak to demonic possession, speculating that the children had been playing with a Ouija board prior to the attacks.
3 Blackburn Fainting Frenzy
During the summer of 1965, over 300 residents of Blackburn, England, suddenly fainted without warning. The incident coincided with Princess Margaret’s scheduled visit to the newly restored Blackburn Cathedral, drawing massive crowds that gathered in the scorching sun. One by one, people collapsed, and ambulance crews attributed the fainting to heat‑induced over‑breathing.
The following day, 98 pupils at St. Hilda’s Girls’ School also experienced abrupt fainting spells. Hospitals were inundated, and mattresses were strewn throughout school hallways to accommodate the influx. An ambulance driver recalled, “As fast as we took them away, new cases from classrooms in other parts of the school were being brought in.”
A year later, a British Medical Journal report by a pediatrician and a London psychologist confirmed the phenomenon as a case of mass hysteria, describing it as an “epidemic of over‑breathing.”
2 Resignation Syndrome
In Sweden, a puzzling condition known as “resignation syndrome” has haunted children of asylum‑seekers for decades. Affected youngsters withdraw completely—unable to open their eyes, speak, or even walk—entering a state of profound catatonia. Dr. Elisabeth Hultcrantz, a volunteer with Doctors of the World, explained, “When I explain to the parents what has happened, I tell them the world has been so terrible that [their child] has gone into herself and disconnected the conscious part of her brain.”
The syndrome first surfaced in the 1990s, with over 400 cases recorded between 2003 and 2005. Pediatrician Karl Sallin of the Astrid Lindgren Children’s Hospital noted, “To our knowledge, no cases have been established outside of Sweden.” By 2016, Sweden’s National Board of Health reported a decline, documenting 169 cases that year.
1 Coca‑Cola Scare
In June 1999, Belgium witnessed a massive panic when more than 100 citizens reported illness after drinking bottled Coca‑Cola. Symptoms ranged from stomach cramps and nausea to headaches and palpitations. The government responded by pulling 30 million cans and bottles from shelves.
An investigation by Belgium’s Health Council concluded the episode was a classic case of mass hysteria. In a public letter, council members wrote, “It is probably significant that a company with such high visibility and symbolic image was involved in this episode. Besides the important role of the media, the scale of the outbreak may have been amplified by the radical measures taken by the health authorities, as well as deficient communication by the Coca‑Cola company.”
Despite the scare, Coca‑Cola rebounded quickly, with sales returning to normal within weeks.