An archaic and no longer used description by doctors for a symptom (or symptoms) with no obvious organic cause, which is an unconscious reaction and from which the person may benefit. It is now recognised as being a dissociative disorder: such disorders – AMNESIA, FUGUE, multiple personality states and trancelike conditions – are powerful defence mechanisms against severe stress when a patient is unable to cope with a particular problem or problems. Symptoms can also mimic physical conditions: for example, apparent paralysis or inability to speak (mutism). ‘Mass hysteria’ is a phenomenon characterised by extreme suggestibility in a group of often emotionally charged people, for example one episode was a belief amongst school pupils that they had a dangerous an illness due to poisoning when in fact they had been subject simply to an unusual concentration of pollen grains in the atmosphere.

Doctors have a duty to make sure there is not an underlying physical disease present to explain the symptoms before diagnosing a dissociative disorder. Most subside spontaneously, but if not, the individual may need psychiatric advice. Treatment is difficult. Reasons for stress should be explored and, if possible, resolved. Hypnosis (see HYPNOTISM) to help the person relive stressful episodes – known as ABREACTION – may be of value.