I.

Introduction

Hysteria, type of mental disorder, in which emotionally laden mental conflicts appear as physical symptoms (called conversion reactions), or as severe mental dissociation. Psychiatric diagnosis of hysteria depends on recognition of a mental conflict and of the unconscious connections between conflict and symptoms. The term mass hysteria is applied to situations in which a large group of people exhibit the same kinds of physical symptoms with no organic cause. For example, one incident of mass hysteria reported in the United States in 1977 involved 57 members of a school marching band who experienced headache, nausea, dizziness, and fainting after a sports event. After a fruitless search for organic causes, researchers concluded that a heat reaction among a few band members had spread by emotional suggestion to other members of the band. However, it must be stressed that this conclusion may have come about because the band members were female (see Study and Treatment below). The term collective stress reaction is now preferred for these situations, which may occur when people are crowded together.