Mass psychogenic illness is characterized by symptoms, occurring among a group of persons with shared beliefs regarding those symptoms, that suggest organic illness but have no identifiable environmental cause and little clinical or laboratory evidence of disease. Mass psychogenic illness typically affects adolescents or children, groups under stress and females disproportionately more than males.
Symptoms often follow an environmental trigger or illness in an index case.
They can spread rapidly by apparent visual transmission, may be aggravated by a prominent emergency or media response, and frequently resolve after patients are separated from each other and removed from the environment in which the outbreak began. Physicians should consider this diagnosis when faced with a cluster of unexplained acute illness. Unfortunately, by the time many outbreaks are recognized as psychogenic illness, they have had a devastating effect on the communities and individuals involved. Mass psychogenic illness, also referred to as mass hysteria, has been described for more than 600 years in a variety of cultures and settings 2,3 but is seldom addressed during medical training. It can be difficult to differentiate from bioterrorism, rapidly spreading infection or acute toxic exposure.