Definitions of psychiatric syndromes--comparison in hospital patients and general population.

Four sets of commonly used 'operational definitions' of psychiatric disorders were applied to clinical information, obtained on the basis of semi-structured interviews with samples of hospital in-patients, out-patients, and general population. The agreement among them in defining 'cases' and in assigning specific diagnostic categories was examined. There was considerable variation among the diagnostic systems in distinguishing between 'cases' and 'non-cases' and in identifying sub-groups of cases as having specific diagnoses. Comparison of operationally defined syndrome categories with diagnoses assigned by clinicians also showed much disagreement.