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Mass psychogenic illness (MPI), also called mass sociogenic illness, mass psychogenic disorder, epidemic hysteria, or mass hysteria, involves the spread of illness symptoms through a population where there is no infectious agent responsible for contagion. It is the rapid spread of illness signs and symptoms affecting members of a cohesive group, originating from a nervous system disturbance involving excitation, loss, or alteration of function, whereby physical complaints that are exhibited unconsciously have no corresponding organic causes.


Causes

MPI is distinct from other types of collective delusions by involving physical symptoms. It is not well understood and its causes are uncertain. Qualities of MPI outbreaks often include: *symptoms that have no plausible organic basis; *symptoms that are transient and benign; *symptoms with rapid onset and recovery; *occurrence in a segregated group; *the presence of extraordinary anxiety; *symptoms that are spread via sight, sound or oral communication; *a spread that moves down the age scale, beginning with older or higher-status people; *a preponderance of female participants. British psychiatrist Simon Wessely distinguishes between two forms of MPI: * ''Mass anxiety hysteria'' "consists of episodes of acute anxiety, occurring mainly in schoolchildren. Prior tension is absent and the rapid spread is by visual contact." * ''Mass motor hysteria'' "consists of abnormalities in motor behaviour. It occurs in any age group and prior tension is present. Initial cases can be identified and the spread is gradual. … e outbreak may be prolonged." While his definition is sometimes adhered to,
Waller, John. "Looking Back: Dancing plagues and mass hysteria." ''The Psychologist'' 22(7) (2009): 644–47. Web. 17 Dec. 2009.
others such as Ali-Gombe et al. of the University of Maiduguri, Nigeria contest Wessely's definition and describe outbreaks with qualities of both mass motor hysteria and mass anxiety hysteria.Ali-Gombe, A. et al. "Mass hysteria: one syndrome or two?" ''British Journal of Psychiatry'' 1997; 170 387–88. Web. 17 Dec. 2009. The DSM-IV-TR does not have specific diagnosis for this condition but the text describing
conversion disorder Conversion disorder (CD), or functional neurologic symptom disorder, is a diagnostic category used in some psychiatric classification systems. It is sometimes applied to patients who present with neurological symptoms, such as numbness, blindness ...
states that "In 'epidemic hysteria', shared symptoms develop in a circumscribed group of people following 'exposure' to a common precipitant."


Common symptoms

Timothy F. Jones of the Tennessee Department of Health compiles the following symptoms based on their commonality in outbreaks occurring in 1980–1990:


Prevalence and intensity

Adolescents and children are frequently affected in cases of MPI. The hypothesis that those prone to extraversion or neuroticism, or those with low IQ scores, are more likely to be affected in an outbreak of hysterical epidemic has not been consistently supported by research. Bartholomew and Wessely state that it "seems clear that there is no particular predisposition to mass sociogenic illness and it is a behavioural reaction that anyone can show in the right circumstances." Intense media coverage seems to exacerbate outbreaks. The illness may also recur after the initial outbreak. John Waller advises that once it is determined that the illness is psychogenic, it should not be given credence by authorities. For example, in the Singapore factory case study, calling in a medicine man to perform an exorcism seemed to perpetuate the outbreak.


Research

Besides the difficulties common to all research involving the social sciences, including a lack of opportunity for controlled experiments, mass sociogenic illness presents special difficulties to researchers in this field. Balaratnasingam and Janca report that the methods for "diagnosis of mass hysteria remain contentious." According to Jones, the effects resulting from MPI "can be difficult to differentiate from
hose of A hose is a flexible hollow tube designed to carry fluids from one location to another. Hoses are also sometimes called ''pipes'' (the word ''pipe'' usually refers to a rigid tube, whereas a hose is usually a flexible one), or more generally ' ...
bioterrorism Bioterrorism is terrorism involving the intentional release or dissemination of biological agents. These agents are bacteria, viruses, insects, fungi, and/or toxins, and may be in a naturally occurring or a human-modified form, in much the sa ...
, rapidly spreading infection or acute
toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subs ...
exposure."
Jones, Timothy. "Mass Psychogenic Illness: Role of the Individual Physician." ''American Family Physician.'' American Family of Family Physicians: 15 Dec. 2000. Web. 28 Nov. 2009.
These troubles result from the residual diagnosis of MPI. There is a lack of logic in an argument that proceeds: "There isn't anything, so it must be MPI." It is an example of an
argument from ignorance Argument from ignorance (from la, argumentum ad ignorantiam), also known as appeal to ignorance (in which ''ignorance'' represents "a lack of contrary evidence"), is a fallacy in informal logic. It asserts that a proposition is true because it ...
, with ''ignorance'' here intended to mean "an absence of contrary evidence". It precludes the notion that an organic factor could have been overlooked (''i.e.'' that there may have been insufficient investigation), or the possibility that the answer may currently be unknown but known at a future point in time. Nevertheless, running an extensive number of tests extends the probability of false positives. Singer, of the Uniformed Schools of Medicine, has summarized the problems with such a diagnosis:Singer, Jerome. "Yes Virginia, There Really Is a Mass Psychogenic Illness." ''Mass Psychogenic Illness: A Social Psychological Analysis.'' Ed. Colligan et al. Hillsdale, NJ: Lawrence Erlbaum Associates, Publishers, 1982. 21–31. Print.
" u find a group of people getting sick, you investigate, you measure everything you can measure … and when you still can't find any physical reason, you say 'well, there's nothing else here, so let's call it a case of MPI.'"


Relationship to autism and mirror neurons

Due to the role of the visual and auditory systems in MPI, a link between MPI and
mirror neurons A mirror neuron is a neuron that fires both when an animal acts and when the animal observes the same action performed by another. Thus, the neuron "mirrors" the behavior of the other, as though the observer were itself acting. Such neurons ha ...
has been suggested. In this context, MPI appears as the neurological opposite of
autism The autism spectrum, often referred to as just autism or in the context of a professional diagnosis autism spectrum disorder (ASD) or autism spectrum condition (ASC), is a neurodevelopmental condition (or conditions) characterized by difficulti ...
, caused by an overactive, not underactive, mirror neuron system. This could in turn explain the gender difference bias observed in these two conditions, with autism predominantly affecting males (persons with autism show diminished activity in the mirror neuron system), and MPI predominantly affecting young girls, which appear have a more sensitive mirror system.


In history


Middle Ages

The earliest studied cases linked with epidemic hysteria are the
dancing mania Dancing mania (also known as dancing plague, choreomania, St. John's Dance, tarantism and St. Vitus' Dance) was a social phenomenon that occurred primarily in mainland Europe between the 14th and 17th centuries. It involved groups of people da ...
s of the Middle Ages, including St. John's dance and
tarantism Tarantism is a form of hysteric behaviour originating in Southern Italy, popularly believed to result from the bite of the wolf spider ''Lycosa tarantula'' (distinct from the broad class of spiders also called tarantulas). A better candidate c ...
. These were supposed to be associated with spirit possession or the bite of the tarantula. Those with dancing mania would dance in large groups, sometimes for weeks at a time. The dancing was sometimes accompanied by stripping, howling, the making of obscene gestures, or even (reportedly) laughing or crying to the point of death. Dancing mania was widespread over Europe. Between the 15th and 19th centuries, instances of motor hysteria were common in
nunneries A convent is a community of monks, nuns, religious brothers or, sisters or priests. Alternatively, ''convent'' means the building used by the community. The word is particularly used in the Catholic Church, Lutheran churches, and the Anglican ...
. The young ladies that made up these convents were sometimes forced there by family. Once accepted, they took vows of chastity and poverty. Their lives were highly regimented and often marked by strict disciplinary action. The nuns would exhibit a variety of behaviors, usually attributed to demonic possession. They would often use crude language and exhibit suggestive behaviors. One convent's nuns would regularly meow like cats. Priests were often called in to
exorcise Exorcism () is the religious or spiritual practice of evicting demons, jinns, or other malevolent spiritual entities from a person, or an area, that is believed to be possessed. Depending on the spiritual beliefs of the exorcist, this may be d ...
demons.


18th to 21st centuries


In factories

MPI outbreaks occurred in factories following the industrial revolution in England, France, Germany, Italy and Russia as well as the United States and Singapore. W. H. Phoon, Ministry of Labour in Singapore, gives a case study of six outbreaks of MPI in Singapore factories between 1973 and 1978. They were characterized by (1) hysterical seizures of screaming and general violence, wherein tranquilizers were ineffective (2) trance states, where a worker would claim to be speaking under the influence of a spirit or '' jinn'' and (3) frightened spells: some workers complained of unprecedented fear, or of being cold, numb, or dizzy. Outbreaks would subside in about a week. Often a ''
bomoh A ''bomoh'' ( sou, โต๊ะบอมอ; ) is a Malay shaman and traditional medicine practitioner. The term is used mainly in Malaysia and parts of Sumatra, whereas most Indonesians use the word ''dukun''. It is often mistranslated into Engl ...
'' (medicine man) would be called in to do a ritual exorcism. This technique was not effective and sometimes seemed to exacerbate the MPI outbreak. Females and
Malay people Malays ( ms, Orang Melayu, Jawi: أورڠ ملايو) are an Austronesian ethnic group native to eastern Sumatra, the Malay Peninsula and coastal Borneo, as well as the smaller islands that lie between these locations — areas that are col ...
were affected disproportionately. Especially notable is the "June Bug" outbreak: In June 1962, a peak month in factory production, 62 workers at a dressmaking factory in a textile town in the Southern United States experienced symptoms including severe nausea and breaking out on the skin. Most outbreaks occurred during the first shift, where four fifths of the workers were female. Of 62 total outbreaks, 59 were women, some of whom believed they were bitten by bugs from a fabric shipment, so
entomologist Entomology () is the scientific study of insects, a branch of zoology. In the past the term "insect" was less specific, and historically the definition of entomology would also include the study of animals in other arthropod groups, such as arach ...
s and others were called in to discover the pathogen, but none was found. Kerchoff coordinated the interview of affected and unaffected workers at the factory and summarizes his findings: * Strain – those affected were more likely to work overtime frequently and provide the majority of the family income. Many were married with children. * Affected persons tended to deny their difficulties. Kerchoff postulates that such were "less likely to cope successfully under conditions of strain." * Results seemed consistent with a model of
social contagion Social contagion involves behaviour, emotions, or conditions spreading spontaneously through a group or network. The phenomenon has been discussed by social scientists since the late 19th century, although much work on the subject was based on un ...
. Groups of affected persons tended to have strong social ties. Kerchoff also links the rapid rate of contagion with the apparent reasonableness of the bug infestation theory and the credence given to it in accompanying news stories. Stahl and Lebedun describe an outbreak of mass sociogenic illness in the
data center A data center (American English) or data centre (British English)See spelling differences. is a building, a dedicated space within a building, or a group of buildings used to house computer systems and associated components, such as telecommuni ...
of a university town in the
United States Midwest The Midwestern United States, also referred to as the Midwest or the American Midwest, is one of four census regions of the United States Census Bureau (also known as "Region 2"). It occupies the northern central part of the United States. I ...
in 1974. Ten of 39 workers smelling an unconfirmed "mystery gas" were rushed to a hospital with symptoms of dizziness, fainting, nausea and vomiting. They report that most workers were young women either putting their husbands through school or supplementing the family income. Those affected were found to have high levels of job dissatisfaction. Those with strong social ties tended to have similar reactions to the supposed gas, which only one unaffected woman reported smelling. No gas was detected in subsequent tests of the data center.


In schools

Mass hysteria affected schools in
Berry, Alabama Berry is a town in Fayette County, Alabama, United States. At the 2010 census the population was 1,148, down from 1,238 at the 2000 census. History The town was named for Thompson Berry, a local landowner. The town incorporated in 1883 as "Berry ...
, and Miami Beach in 1974, with the former episode taking the form of recurring
pruritus Itch (also known as pruritus) is a sensation that causes the desire or reflex to scratch. Itch has resisted many attempts to be classified as any one type of sensory experience. Itch has many similarities to pain, and while both are unpleasant ...
, and the latter initially triggering fears of poison gas (it was traced back to a popular student who happened to be sick with a virus). Thousands were affected by the spread of a supposed illness in a province of Kosovo in March to June 1990, exclusively affecting
ethnic Albanians The Albanians (; sq, Shqiptarët ) are an ethnic group and nation native to the Balkan Peninsula who share a common Albanian Cultural heritage, ancestry, Albanian culture, culture, Albanian history, history and Albanian language, language. ...
, most of whom were young adolescents.Radovanovic, Z. "On the Origin of Mass Casualty Incidents in Kosovo, Yugoslavia, in 1990." ''European Journal of Epidemiology'' 12(1) (1996):101–113. JSTOR. Web. 27 Nov. 2009. A wide variety of symptoms were manifested, including headache, dizziness, impeded respiration, weakness/adynamia, burning sensations, cramps, retrosternal/chest pain, dry mouth and nausea. After the illness had subsided, a bipartisan Federal Commission released a document, offering the explanation of psychogenic illness. Radovanovic of the Department of Community Medicine and Behavioural Sciences Faculty of Medicine in Safat, Kuwait reports:
This document did not satisfy either of the two ethnic groups. Many Albanian doctors believed that what they had witnessed was an unusual epidemic of poisoning. The majority of their Serbian colleagues also ignored any explanation in terms of psychopathology. They suggested that the incident was faked with the intention of showing Serbs in a bad light but that it failed due to poor organization.
Rodovanovic expects that this reported instance of mass sociogenic illness was precipitated by the demonstrated volatile and culturally tense situation in the province. The Tanganyika laughter epidemic of 1962 was an outbreak of laughing attacks rumored to have occurred in or near the village of Kanshasa on the western coast of Lake Victoria in the modern nation of Tanzania, eventually affecting 14 different schools and over 1,000 people. On the morning of Thursday 7 October 1965, at a girls' school in
Blackburn Blackburn () is an industrial town and the administrative centre of the Blackburn with Darwen borough in Lancashire, England. The town is north of the West Pennine Moors on the southern edge of the Ribble Valley, east of Preston and north- ...
in England, several girls complained of dizziness. Some fainted. Within a couple of hours, 85 girls from the school were rushed by ambulance to a nearby hospital after fainting. Symptoms included swooning, moaning, chattering of teeth,
hyperpnea Hyperpnea, or hyperpnoea (forced respiration) is increased volume of air taken during breathing. It can occur with or without an increase in respiration rate. It is characterized by deep breathing. It may be physiologic—as when required by oxygen ...
, and
tetany Tetany or tetanic seizure is a medical sign consisting of the involuntary contraction of muscles, which may be caused by disorders that increase the action potential frequency of muscle cells or the nerves that innervate them. Muscle cramps cau ...
. Moss and McEvedy published their analysis of the event about one year later. Their conclusions follow. Note that their conclusion about the above-average
extraversion The traits of extraversion (also spelled extroversion Retrieved 2018-02-21.) and introversion are a central dimension in some human personality theories. The terms ''introversion'' and ''extraversion'' were introduced into psychology by Carl J ...
and neuroticism of those affected is not necessarily typical of MPI: *Clinical and laboratory findings were essentially negative. *Investigations by the public health authorities did not uncover any evidence of pollution of food or air. *The epidemiology of the outbreak was investigated by means of questionnaires administered to the whole school population. It was established that the outbreaks began among the 14-year-olds, but that the heaviest incidence moved to the youngest age groups. *By using the Eysenck Personality Inventory, it was established that, in all age groups, the mean E xtraversionand N euroticismscores of the affected were higher than those of the unaffected. *The younger girls proved more susceptible, but disturbance was more severe and lasted longer in the older girls. *It was considered that the epidemic was hysterical, that a previous polio epidemic had rendered the population emotionally vulnerable, and that a three-hour parade, producing 20 faints on the day before the first outbreak, had been the specific trigger. *The data collected were thought to be incompatible with organic theories and with the compromise theory of an organic nucleus. Another possible case occurred in Belgium in June 1999 when people, mainly schoolchildren, became ill after drinking Coca-Cola. In the end, scientists were divided over the scale of the outbreak, whether it fully explains the many different symptoms and the scale to which sociogenic illness affected those involved. A possible outbreak of mass psychogenic illness occurred at Le Roy Junior-Senior High School in 2011, in
upstate New York Upstate New York is a geographic region consisting of the area of New York State that lies north and northwest of the New York City metropolitan area. Although the precise boundary is debated, Upstate New York excludes New York City and Long Is ...
, US, in which multiple students began having symptoms similar to
Tourette syndrome Tourette syndrome or Tourette's syndrome (abbreviated as TS or Tourette's) is a common neurodevelopmental disorder that begins in childhood or adolescence. It is characterized by multiple movement (motor) tics and at least one vocal (phonic ...
. Various health professionals ruled out such factors as
Gardasil Gardasil is an HPV vaccine for use in the prevention of certain strains of human papillomavirus (HPV). Text was copied from this source which is copyright European Medicines Agency. Reproduction is authorized provided the source is acknowledge ...
, drinking water contamination, illegal drugs, carbon monoxide poisoning and various other potential environmental or infectious causes, before diagnosing the students with a
conversion disorder Conversion disorder (CD), or functional neurologic symptom disorder, is a diagnostic category used in some psychiatric classification systems. It is sometimes applied to patients who present with neurological symptoms, such as numbness, blindness ...
and mass psychogenic illness. Starting around 2009, a spate of apparent poisonings at girls' schools across Afghanistan began to be reported; symptoms included dizziness, fainting and vomiting. The
United Nations The United Nations (UN) is an intergovernmental organization whose stated purposes are to maintain international peace and security, develop friendly relations among nations, achieve international cooperation, and be a centre for harmonizi ...
, World Health Organization and NATO's International Security Assistance Force carried out investigations of the incidents over multiple years, but never found any evidence of toxins or poisoning in the hundreds of blood, urine and water samples they tested. The conclusion of the investigators was that the girls were experiencing a mass psychogenic illness. In August 2019 the BBC reported that schoolgirls at the Ketereh national secondary school (SMK Ketereh) in
Kelantan Kelantan (; Jawi: ; Kelantanese Malay: ''Klate'') is a state in Malaysia. The capital is Kota Bharu and royal seat is Kubang Kerian. The honorific name of the state is ''Darul Naim'' (Jawi: ; "The Blissful Abode"). Kelantan is located in th ...
, Malaysia, started screaming, with some claiming to have seen 'a face of pure evil'. Dr Simon Wessely of
King's College Hospital King's College Hospital is a major teaching hospital and major trauma centre in Denmark Hill, Camberwell in the London Borough of Lambeth, referred to locally and by staff simply as "King's" or abbreviated internally to "KCH". It is managed by ...
, London suggested it was a form of 'collective behaviour'. Robert Bartholomew, an American medical sociologist and author, said, "It is no coincidence that Kelantan, the most religiously conservative of all Malaysian states, is also the one most prone to outbreaks." This view is supported by Afiq Noor, an academic, who argues that the stricter implementation of Islamic law in school in states such as Kelantan is linked to the outbreaks. He suggested that the screaming outbreak was caused by the constricted environment. In Malaysian culture burial sites and trees are common settings for supernatural tales about the spirits of dead infants (''toyol''), vampiric ghosts ''(pontianak)'' and vengeful female spirits (''penanggalan).'' Authorities responded to the Kelantan outbreak by cutting down trees around the school. Outbreaks of mass psychogenic illness "have been reported in Catholic convents and monasteries across Mexico, Italy and France, in schools in Kosovo and even among cheerleaders in a rural North Carolina town". Episodes of mass hysteria has been observed in schools of Nepal frequently, even leading to closure of schools temporarily. A unique phenomenon of “recurrent epidemic of mass hysteria” was reported from a school of Pyuthan district of western Nepal in 2018. After a 9-year-old school girl developed crying and shouting episodes, quickly other children of the same school were also affected resulting in 47 affected students (37 females, 10 males) in the same day. Since 2016 similar episodes of mass psychogenic illness has been occurring in the same school every year. This is thought to be a unique case of recurrent mass hysteria. In July 2022 reports of up to 15 girls showing unusual symptoms such as screaming, trembling, and banging their heads came up from a government school in
Bageshwar Bageshwar ( Kumaoni: ''Bāgshyār'') is a town and a municipal board in Bageshwar district in the state of Uttarakhand, India. It is located at a distance of 470 km from the National Capital New Delhi and 332 km from the State Capit ...
, Uttarakhand. Mass psychological illness has been suggested as a possible cause.


Terrorism and biological warfare

Bartholomew and Wessely anticipate the "concern that after a chemical, biological or nuclear attack, public health facilities may be rapidly overwhelmed by the anxious and not just the medical and psychological casualties." Additionally, early symptoms of those affected by MPI are difficult to differentiate from those actually exposed to the dangerous agent. The first Iraqi missile hitting Israel during the Persian Gulf War was believed to contain chemical or biological weapons. Though this was not the case, 40% of those in the vicinity of the blast reported breathing problems. Right after the 2001 anthrax attacks in the first two weeks of October 2001, there were over 2300 false anthrax alarms in the United States. Some reported physical symptoms of what they believed to be anthrax. Also in 2001, a man sprayed what was later found to be a
window cleaner Window cleaning, or window washing, is the exterior cleaning of architectural glass used for structural, lighting, or decorative purposes. It can be done manually, using a variety of tools for cleaning and access. Technology is also employed an ...
into a subway station in Maryland. Thirty-five people were treated for nausea, headaches and sore throats. In 2017, some employees of the US embassy in Cuba reported symptoms (nicknamed the " Havana syndrome") attributed to "sonic attacks". The following year, some US government employees in China reported similar symptoms. Some scientists have suggested the alleged symptoms were psychogenic in nature. However, one study using
neuroimaging Neuroimaging is the use of quantitative (computational) techniques to study the structure and function of the central nervous system, developed as an objective way of scientifically studying the healthy human brain in a non-invasive manner. Incre ...
suggest at least some organic, non-
psychogenic A psychogenic effect is one that originates from the brain instead of other physical organs (i.e. the cause is psychological rather than physiological) and may refer to: *Psychogenic pain *Psychogenic disease *Psychogenic amnesia Psychogenic am ...
cause.


Children in recent refugee families

Refugee children in Sweden have been reported to fall into coma-like states on learning their families will be deported. The condition, known as resignation syndrome ( sv, uppgivenhetssyndrom), is believed to only exist among the refugee population in the Scandinavian country, where it has been prevalent since the early part of the 21st century. Commentators state "a degree of psychological contagion" is inherent to the condition, by which young friends and relatives of the affected individual can also come to have the condition. In a 130-page report on the condition, commissioned by the government and published in 2006, a team of psychologists, political scientists and sociologists hypothesized that it was a
culture-bound syndrome In medicine and medical anthropology, a culture-bound syndrome, culture-specific syndrome, or folk illness is a combination of psychiatric and somatic symptoms that are considered to be a recognizable disease only within a specific society or ...
, a psychological illness endemic to a specific society. This phenomenon has later been called into question, with children witnessing that they were forced, by their parents, to act in a certain way in order to increase chances of being granted residence permits. As evidenced by medical records, healthcare professionals were aware of this scam, and witnessed parents who actively refused aid for their children, but remained silent. Later, Sveriges Television, Sweden's national public television broadcaster, were severely critiqued by investigative journalist Janne Josefsson for failing to uncover the truth.


Internet

After the rise of a popular breakthrough YouTube channel in 2019 where the presenter exhibits extensive
Tourette's Tourette syndrome or Tourette's syndrome (abbreviated as TS or Tourette's) is a common neurodevelopmental disorder that begins in childhood or adolescence. It is characterized by multiple movement (motor) tics and at least one vocal (phonic) ...
-like behaviour, there was a sharp rise in young people referred to clinics specializing in tics, thought to be related to
social contagion Social contagion involves behaviour, emotions, or conditions spreading spontaneously through a group or network. The phenomenon has been discussed by social scientists since the late 19th century, although much work on the subject was based on un ...
spread via the internet, and also to stress from
eco-anxiety Eco-anxiety (short for ecological anxiety and also known as eco-distress or climate-anxiety) has been defined as "a chronic fear of environmental doom". Extensive studies had been done on ecological anxiety since 2007, and various definitions remai ...
and the COVID-19 pandemic. The authors of an August 2021 report found evidence that social media was the primary vector for transmission and that it predominantly affects adolescent girls, declaring the phenomenon the first recorded instance of "mass social media–induced illness" (MSMI).


See also

* * * * * , one example of satanic panic * (from the French for "a madness shared by two") * * * * () * () * *


Notes


References


General references

*Ali-Gombe, A. et al. "Mass hysteria: one syndrome or two?" ''British Journal of Psychiatry'' 1997; 170 387–78. Web. 17 Dec. 2009. *Balaratnasingam, Sivasankaran and Aleksandar Janca. "Mass hysteria revisited." ''Current Opinion in Psychiatry'' 19(2) (2006): 171–74. ''Research Gate.'' Web. 28 Nov. 2009. *Bartholomew, Robert. ''Little Green Men, Meowing Nuns and Head-Hunting Panics.'' Jefferson, North Carolina: McFarland & Company, Inc. Publishers. 2001. Print. *Bartholomew, Robert and Simon Wessely. "Protean nature of mass sociogenic illness." ''The British Journal of Psychiatry'' 2002; 180: 300–06. Web. 28 Nov. 2009

*Jones, Timothy. "Mass Psychogenic Illness: Role of the Individual Physician." ''American Family Physician.'' American Family of Family Physicians: 15 Dec. 2000. Web. 28 Nov. 2009

*Kerchoff, Alan C. "Analyzing a Case of Mass Psychogenic Illness." ''Mass Psychogenic Illness: A Social Psychological Analysis.'' Ed. Colligan et al. Hillsdale, NJ: Lawrence Erlbaum Associates, Publishers, 1982. 5–19. Print. *Mass, Weir E. "Mass sociogenic illness." ''CMAJ'' 2005; 172: 36. Web. 14 Dec. 2009

*Moss, P. D. and C. P. McEvedy. "An epidemic of overbreathing among schoolgirls." ''British Medical Journal'' 2(5525) (1966):1295–1300. Web. 17 Dec. 2009. *Phoon, W. H. "Outbreaks of Mass Hysteria at Workplaces in Singapore: Some Patterns and Modes of Presentation." ''Mass Psychogenic Illness: A Social Psychological Analysis.'' Ed. Colligan et al. Hillsdale, NJ: Lawrence Erlbaum Associates, Publishers, 1982. 21–31. Print. * *Singer, Jerome. "Yes Virginia, There Really Is a Mass Psychogenic Illness." ''Mass Psychogenic Illness: A Social Psychological Analysis.'' Ed. Colligan et al. Hillsdale, NJ: Lawrence Erlbaum Associates, Publishers, 1982. 21–31. Print. * * * * * {{Conspiracy theories Mass psychogenic illness, Group processes Somatic symptom disorders Crowd psychology Social phenomena Behavioral addiction