Evolution of diagnostic criteria in psychoses.

The term psychosis was first introduced in the mid-19th century for the separation of psychiatric disorders from neurological disorders within the neuroses. The concept of psychosis has become gradually restricted from a generic term for psychiatric disorders to one of the major classes of mental illness, which was assumed to be the result of a disease process, and, more recently, to a symptom present in many psychiatric disorders. In the course of this development, the díagnostic criteria for psychosis shifted from the severity of the clinical manifestations and the degree of impairment in social functioning to the presence of one or more symptoms in a set of psychopathological symptoms, which include hallucinations, formal thought disorder manifest in disorganized or odd speech, delusions, flat/inappropriate affect, avolition/apathy disorganized behavior, catatonic motor behavior, and depersonalization/derealization. The changes in the conceptualization of psychosis and in the diagnostic criteria for psychosis are documented in the various editions of the Diagnostic and Statistical Manual of Mental Disorders of the American Psychiatric Assocíation (from DSM-I to DSM-IV] and the International Classification of Diseases of the World Health Organization (from ICD-9 to ICD-10].