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Mass psychogenic illness (MPI), also called mass sociogenic illness or just sociogenic illness,〔(), Mass, Weir E. "Mass sociogenic illness". ''CMAJ'' 172 (2005): 36. Web. 14 Dec. 2009.〕 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 aetiology."〔() Bartholomew, Robert and Simon Wessely. "Protean nature of mass sociogenic illness." ''The British Journal of Psychiatry'' 180 (2002): 300–306. Web. 28 Nov. 2009.〕 MPI is distinct from other collective delusions, also included under the blanket terms of mass hysteria, in that MPI causes symptoms of disease, though there is no organic cause. There is a clear preponderance of female victims.〔 The DSM-IV-TR does not have specific diagnosis for this condition but the text describing conversion disorder states that "In 'epidemic hysteria', shared symptoms develop in a circumscribed group of people following 'exposure' to a common precipitant." == Current state of research == According to Balaratnasingam and Janca, “mass hysteria is to date a poorly understood condition. Little certainty exists regarding its etiology.”〔 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 remains contentious.〔Balaratnasingam, Sivasankaran and Aleksandar Janca. “Mass hysteria revisited.” ''Current opinion in psychiatry'' 19(2) (2006): 171–4. Research Gate. Web. 28 Nov. 2009.〕 According to Timothy Jones of the Tennessee Department of Public Health, MPI “can be difficult to differentiate from bioterrorism, rapidly spreading infection or acute toxic 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. Singer, of the Uniformed Schools of Medicine, puts the problems with such a diagnosis thus:〔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.〕 “()ou 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.'” There is a lack of logic in an argument that proceeds: “There isn't anything, so it must be MPI.” It precludes the notion that an organic factor could have been overlooked. Nevertheless, running an extensive number of tests extends the probability of false positives.〔 British psychologist Wesseley distinguishes between two forms of MPI:〔Wessely, Simon. “Mass hysteria: two syndromes?” ''Psychological Medicine'' 17(1) (1987):109–20. Web. 16 Dec. 2009.〕 # 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. . . . ()he 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): 644–7. Web. 17 Dec. 2009.〕 others such as Ali-Gombe et al. of the University of Maiduguri, Nigeria contest Wesseley'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'' 170 (1997) 387–8. Web. 17 Dec. 2009.〕 An evolutionary psychology explanation for this disorder, as well as for conversion disorder more generally, is that the symptom may have been evolutionary advantageous during warfare. A non-combatant with these symptoms signals non-verbally, possibly to someone speaking a different language, that she or he is not dangerous as a combatant and also may be carrying some form of dangerous infectious disease. This can explain that conversion disorder may develop following a threatening situation, that there may be a group effect with many people simultaneously developing similar symptoms, and the gender difference in prevalence. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Mass psychogenic illness」の詳細全文を読む スポンサード リンク
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