Defining schizophrenia: Operational criteria

Abstract

The use of operational criteria to define the syndrome of schizophrenia has dramatically improved the reliability of diagnosis. However, none of the many different operational definitions for schizophrenia has proven superior validity and it is therefore suggested that a polydiagnostic appproach is adopted until the aetiology of schizophrenia is determined and consequently most valid definition known. The operational criteria checklist for psychotic illness (OPCRIT) facilitates such a polydiagnostic approach and the paper goes on to describe the use of OPCRIT on various data sets of psychotic subjects to explore three further questions. The first of these considers the relationship between different definitions. The second question relates to which other psychotic disorders and personality types might be included within a broader schizophrenia spectrum and the third question considered relates to the different sub-types of disorder found in schizophrenia and whether these are aetiologically separate or merely quantitative differences.