Mass psychogenic illness, also known as mass sociogenic illness, mass psychogenic disorder, epidemic hysteria, or mass hysteria, occurs when symptoms of illness spread among a group of people without any infectious disease causing the spread. It happens quickly within a group of people who are connected or share a close relationship. The symptoms come from problems in the nervous system, such as overactivity, loss, or changes in function. These physical symptoms appear without the person realizing it and have no known physical or organic reasons.

Signs and symptoms

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

Causes and risk factors

Mass Psychogenic Illness (MPI) is different from other types of shared or group delusions because it includes physical symptoms. Common features of MPI outbreaks often include:

• symptoms with no clear physical cause;
• symptoms that are short-term and not harmful;
• symptoms that appear quickly and improve quickly;
• occurrence in a group that is separated from others;
• high levels of fear or worry;
• symptoms that spread through seeing, hearing, or speaking to others;
• spread that moves from older or higher-status people to younger individuals.

British psychiatrist Simon Wessely identifies two types of MPI:

• Mass Anxiety Hysteria: "Involves sudden, short-term anxiety, mostly in schoolchildren. No prior stress is present, and the spread happens quickly through seeing others."
• Mass Motor Hysteria: "Involves problems with movement. It can happen at any age, and some stress is present before the outbreak. The first cases can be identified, and the spread is slow. The outbreak may last a long time."

While some researchers use Wessely’s definitions, others argue that outbreaks can have traits of both types of MPI.

The DSM-IV-TR does not provide a specific diagnosis for MPI. However, it describes conversion disorder, stating that "In 'epidemic hysteria,' shared symptoms appear in a small group of people after being exposed to a common event."

MPI cases often affect children and teenagers, with girls being more likely to be impacted. Research has not consistently shown that people with certain personality traits, such as being very outgoing or anxious, or those with lower IQ scores, are more likely to be affected. Bartholomew and Wessely note that "it seems clear that no specific group is more likely to experience mass sociogenic illness, and it is a behavior that anyone may show under the right conditions."

Strong media attention may worsen outbreaks. The illness can also return after the initial outbreak. John Waller suggests that once an illness is determined to be psychogenic, authorities should not give it serious attention. For example, in the Singapore factory case study, calling in a medicine man to perform an exorcism seemed to make the outbreak worse.

History

The earliest studied cases linked to epidemic hysteria are the dancing manias of the Middle Ages, including St. John's dance and tarantism. These were thought to be caused by spirit possession or the bite of the tarantula. People with dancing mania would dance in large groups, sometimes for weeks at a time. The dancing was sometimes accompanied by stripping, shouting, making rude gestures, or laughing or crying so intensely that it led to death. Dancing mania was common across 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. Once inside, they took vows of chastity and poverty. Their lives were very strict, with frequent discipline. The nuns showed behaviors that were usually blamed on demonic possession. They sometimes used harsh language and acted in ways that seemed suggestive.

In the English version of Hecker’s The Epidemics of the Middle Ages (1844), the translator Benjamin Guy Babington added a personal note about hysteria. He mentioned reading an uncited French medical journal that described a convent in France where nuns began meowing like cats one day. The nuns meowed for long periods throughout the day until they were beaten with rods to stop.

Priests were often called in to perform exorcisms to drive out demons.

Mass psychogenic illness (MPI) outbreaks occurred in factories after the industrial revolution (1760–1840) in England, France, Germany, Italy, Russia, the United States, and Singapore.

W. H. Phoon, a labor official in Singapore, reported six MPI outbreaks in factories between 1973 and 1978. These were marked by (1) screaming and violent behavior that could not be calmed by tranquilizers, (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 an exorcism. This method was not effective and sometimes made the outbreaks worse. Women and Malay people were more likely to be affected.

One notable 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 four-fifths of the workers were women. Of the 62 total cases, 59 were women. Some believed they were bitten by bugs from a fabric shipment. Scientists were brought in to find the cause, but no pathogen was discovered.

Kerchoff interviewed affected and unaffected workers and found:
– Affected workers often worked overtime and were the main earners for their families. Many were married with children.
– Affected workers often denied their problems. Kerchoff suggested they were "less likely to cope with stress."
– Results supported a model of social contagion, where people with strong social ties were more likely to share similar symptoms.

Kerchoff linked the fast spread of the illness to the plausibility of the "bug infestation" theory and how it was reported in the news.

In 1974, Stahl and Lebedun described an MPI outbreak at a university data center in the United States Midwest. Ten of 39 workers who smelled an unconfirmed "mystery gas" were hospitalized with dizziness, fainting, nausea, and vomiting. Most affected workers were young women, either supporting their husbands’ education or helping their families financially. Those affected had high levels of job dissatisfaction. People with strong social ties often had similar reactions to the supposed gas, 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, Tanzania, and spread to 14 schools, affecting over 1,000 people.

On October 7, 1965, several girls at a school in Blackburn, England, complained of dizziness. Some fainted, and within hours, 85 girls were taken to the hospital. Symptoms included fainting, moaning, chattering teeth, rapid breathing, and muscle spasms. Moss and McEvedy later studied the event. They found:
– No evidence of food or air pollution was found.
– The outbreak started among 14-year-olds but spread to younger students.
– Affected students scored higher in extraversion and neuroticism compared to unaffected students.
– Younger girls were more likely to be affected, but older girls had more severe and longer-lasting symptoms.
– The epidemic was considered hysterical, possibly triggered by a parade the day before the outbreak.

In 1974, mass hysteria affected schools in Berry, Alabama, and Miami Beach. In Berry, it caused recurring itches. In Miami Beach, it began with fears of poison gas, later traced to a sick student.

In March to June 1990, thousands of ethnic Albanian adolescents in Kosovo experienced symptoms like headaches, dizziness, chest

Society and culture

In 2019, a well-known YouTube channel featuring a person who shows symptoms similar to Tourette's syndrome became popular. This led to a sudden increase in young people being referred to clinics that treat tics, which experts believe may be linked to the spread of behaviors through the internet, as well as stress caused by concerns about the environment 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 most often affected teenage girls. The report described this as 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 difficulty of conducting controlled experiments. Balaratnasingam and Janca note that diagnosing mass hysteria is still debated among experts. Jones explains that the effects of MPI can be hard to tell apart from those caused by bioterrorism, quickly spreading infections, or exposure to harmful substances.

These challenges arise because MPI is often diagnosed by ruling out other causes. This approach can lead to flawed reasoning, such as claiming, "There is no evidence for anything else, so it must be MPI." This is an example of an "argument from ignorance," meaning a conclusion based on a lack of evidence against it. This reasoning ignores the possibility that an unknown medical cause might have been missed or that the answer might become clear later. However, performing many tests increases the chance of finding false positives. Singer, from the Uniformed Schools of Medicine, has described these issues:

MPI involves the visual and auditory systems, leading some researchers to link it to mirror neurons in the brain. In this context, MPI is seen as the opposite of autism, which is associated with underactive mirror neurons. Autism is more common in males, while MPI is more common in young girls. This difference may be explained by the fact that girls tend to have more sensitive mirror neuron systems.