Mass psychogenic illness (MPI), also called mass sociogenic illness, mass psychogenic disorder, epidemic hysteria, or mass hysteria, 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.
Etiology
Mass psychogenic illness involves the spread of illness symptoms through a population where there is no infectious agent responsible for contagion. [Source: Wikipedia 
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