Hysteria: Historical term for a chronic, but fluctuating, disorder beginning in early life and characterized by recurrent and multiple somatic complaints not apparently due to physical illness. This diagnosis is not used in contemporary practice.Conversion Disorder: A disorder whose predominant feature is a loss or alteration in physical functioning that suggests a physical disorder but that is actually a direct expression of a psychological conflict or need.Psychophysiologic Disorders: A group of disorders characterized by physical symptoms that are affected by emotional factors and involve a single organ system, usually under AUTONOMIC NERVOUS SYSTEM control. (American Psychiatric Glossary, 1988)History, 19th Century: Time period from 1801 through 1900 of the common era.Catatonia: A neuropsychiatric disorder characterized by one or more of the following essential features: immobility, mutism, negativism (active or passive refusal to follow commands), mannerisms, stereotypies, posturing, grimacing, excitement, echolalia, echopraxia, muscular rigidity, and stupor; sometimes punctuated by sudden violent outbursts, panic, or hallucinations. This condition may be associated with psychiatric illnesses (e.g., SCHIZOPHRENIA; MOOD DISORDERS) or organic disorders (NEUROLEPTIC MALIGNANT SYNDROME; ENCEPHALITIS, etc.). (From DSM-IV, 4th ed, 1994; APA, Thesaurus of Psychological Index Terms, 1994)Mass Behavior: Collective behavior of an aggregate of individuals giving the appearance of unity of attitude, feeling, and motivation.MMPI: A personality inventory consisting of statements to be asserted or denied by the individual. The patterns of response are characteristic of certain personality attributes.Negativism: State of mind or behavior characterized by extreme skepticism and persistent opposition or resistance to outside suggestions or advice. (APA, Thesaurus of Psychological Index Terms, 1994)Neurology: A medical specialty concerned with the study of the structures, functions, and diseases of the nervous system.History, 20th Century: Time period from 1901 through 2000 of the common era.