Mass psychogenic illness, also called mass sociogenic illness, mass psychogenic disorder, epidemic hysteria, or mass hysteria, happens when symptoms of illness spread among a group of people without a germ or infection causing it. This occurs quickly in a group that is closely connected, starting with a problem in the nervous system that changes how the body works. The physical symptoms shown by people are not caused by any known physical issues in the body.

Signs and symptoms

Timothy F. Jones from the Tennessee Department of Health gathered the following symptoms based on how often they happened during outbreaks between 1980 and 1990.

Causes and risk factors

MPI is different from other types of collective or mass delusions because it includes physical symptoms. Common features of MPI outbreaks are:

British psychiatrist Simon Wessely identifies two types of MPI:

However, some experts disagree and note that outbreaks can have traits of both mass motor hysteria and mass anxiety hysteria.

The DSM-IV-TR does not have a specific diagnosis for MPI. However, it mentions that in "epidemic hysteria," people in a group may share symptoms after a common event.

MPI cases often involve children and teenagers, with girls being more commonly affected. Some theories suggest that people with certain personality traits or lower IQs might be more likely to be affected, but research has not consistently supported this. Bartholomew and Wessely say that there's no specific group more likely to get MPI; it's a reaction that anyone can have under the right conditions.

Strong media coverage can make outbreaks worse. The illness might come back after the first outbreak. John Waller advises that if the illness is psychogenic, authorities should not believe it. For example, in Singapore's factory case, using a medicine man for an exorcism seemed to make the outbreak worse.

History

The earliest studied cases connected to epidemic-related hysteria are the dancing manias of the Middle Ages, such as St. John's dance and tarantism. These were believed to be caused by spirit possession or the bite of a tarantula. People with dancing mania would dance in large groups, sometimes for weeks. The dancing was sometimes followed by stripping, shouting, making rude gestures, or laughing or crying until they became very ill. Dancing mania was common throughout Europe.

Between the 15th and 19th centuries, motor hysteria was often seen in nunneries. Many young women in these convents were sent there by their families. After joining, they took vows of chastity and poverty. Their lives were strictly scheduled and often included harsh punishments. Nuns sometimes showed behaviors that were thought to be caused by demons. They might use rough language or act in suggestive ways.

In the English version of Hecker’s The Epidemics of the Middle Ages (1844), the translator Benjamin Guy Babington added a note about a French convent where nuns began meowing like cats. The nuns meowed for long periods until they were punished with rods to stop them.

Priests were often called to perform exorcisms to remove demons.

Mass psychogenic illness (MPI) outbreaks happened in factories after the Industrial Revolution (1760–1840) in countries like England, France, Germany, Italy, Russia, the United States, and Singapore.

W. H. Phoon, a labor official in Singapore, described six MPI outbreaks in Singapore factories between 1973 and 1978. These outbreaks had three main symptoms: (1) screaming and violent behavior that did not respond to medicine, (2) trance states where workers claimed to speak under the influence of spirits or jinn, and (3) sudden fear, coldness, numbness, or dizziness. Outbreaks usually lasted about a week. Often, a bomoh (a traditional healer) was called to perform a ritual, but this did not help and sometimes made the situation worse. Women and Malay people were more likely to be affected.

One famous case was the "June Bug" outbreak in 1962. At a dressmaking factory in the southern United States, 62 workers experienced severe nausea and skin rashes. Most outbreaks happened during the first shift, where most workers were female. Of the 62 total cases, 59 were women, some of whom believed they were bitten by bugs from a fabric shipment. Scientists were called to find a pathogen, but none was found.

Kerchoff interviewed workers at the factory and found that the fast spread of illness was linked to the belief in the bug infestation, which was supported by news stories.

In 1974, Stahl and Lebedun described an MPI outbreak in a university data center in the U.S. Midwest. Ten of 39 workers who smelled an unconfirmed "mystery gas" were hospitalized with symptoms like dizziness, fainting, and vomiting. Most affected workers were young women who were either supporting their husbands’ education or helping their families earn money. These workers had high levels of job dissatisfaction. People with strong social connections often had similar reactions to the gas, even though only one unaffected woman reported smelling it. No gas was found in tests of the data center.

In 1962, the Tanganyika laughter epidemic began in or near the village of Kanshasa in Tanzania. It spread to 14 schools and affected over 1,000 people.

On October 7, 1965, at a girls’ school in Blackburn, England, several girls reported dizziness and fainted. Within hours, 85 girls were taken to the hospital with symptoms like fainting, moaning, chattering teeth, rapid breathing, and muscle spasms. Moss and McEvedy later studied the event and noted that those affected had higher levels of extraversion and neuroticism than usual, though this is not typical of all MPI cases.

In 1974, mass hysteria occurred in schools in Berry, Alabama, and Miami Beach. In Berry, it caused recurring itches, while in Miami Beach, it started with fears of poison gas. The cause was traced to a sick student who had a virus.

In March to June 1990, thousands of ethnic Albanian teenagers in Kosovo experienced symptoms like headaches, dizziness, chest pain, and nausea. A commission later concluded the illness was psychogenic. However, many Albanian doctors believed it was a poisoning, while some Serbian doctors thought it was staged to harm Serbs’ reputation. Radovanovic, a medical researcher, said the outbreak was linked to the tense and unstable situation in Kosovo.

In June 1999, many schoolchildren in Belgium became ill after drinking Coca-Cola. Scientists disagreed about whether the illness was fully explained by the event or if sociogenic illness played a role.

Starting in 2009, reports of mass poisonings at girls’ schools in Afghanistan emerged. Symptoms included dizziness, fainting, and vomiting. Investigations by the United Nations, World Health Organization, and NATO found no toxins or poisons in samples tested. Investigators concluded the girls had mass psychogenic illness.

In 2011, students at Le Roy Junior-Senior High School in New York had symptoms similar to Tourette syndrome. Doctors ruled out causes like Gardasil, water contamination, drugs, or carbon monoxide poisoning. They diagnosed the students with conversion disorder and mass psychogenic illness.

In August 2019, the BBC reported that schoolgirls at SMK Ketereh in Malaysia began screaming and claimed to see "a face of pure evil." Simon Wessely of King’s College Hospital suggested this was a form of "collective behavior." Robert Bartholomew, a medical sociologist, also studied the event.

Society and culture

In 2019, a popular YouTube channel featuring a presenter who showed symptoms similar to Tourette's disease led to an increase in young people being sent to clinics that treat tics. This rise is believed to be connected to the spread of behaviors through the internet, as well as stress caused by eco-anxiety and the COVID-19 pandemic. A report from August 2021 found that social media was the main way these Tourette's-like behaviors spread, and that they mainly affected teenage girls. The report called this phenomenon the first known case of a mass social media-induced illness (MSMI).

Research

Research on mass psychogenic illness (MPI) or mass sociogenic illness (MSI) faces challenges beyond those common to social science studies, such as the lack of controlled experiments. Balaratnasingam and Janca note that diagnosing mass hysteria remains debated. Jones explains that the effects of MPI can be hard to tell apart from those caused by bioterrorism, fast-spreading infections, or sudden exposure to harmful substances.

These challenges often come from diagnosing MPI when no clear cause is found. A common mistake is assuming something is MPI simply because no other cause has been identified. This is an example of an "argument from ignorance," which means concluding something is true because there is no evidence against it. This approach ignores the possibility that a physical cause might have been missed or that the answer might not yet be known. However, running many tests can also lead to false positives. Singer, from the Uniformed Schools of Medicine, explains this issue:

You find a group of people who are sick, you check everything you can, and if you still can’t find a physical cause, you might say, “Well, there’s nothing else, so it must be MPI.”

Because MPI involves the visual and auditory systems, some researchers suggest a connection to mirror neurons. In this context, MPI is seen as the opposite of autism, which is linked to underactive mirror neurons. This might explain why autism is more common in males and MPI is more common in young girls, as girls may have more sensitive mirror neuron systems.