Classification of schizophrenic psychoses

Abstract

There is a substantial need, based on the heuristic principle, to arrive at a valid classification of schizophrenic psychoses. According to the modern theory of science bases on critical rationalism, nosological classifications in psychiatry are regarded as "useful" conventions requiring precise operational definitions. There are several methods of classification, typological classifications having gained widest acceptance in nosology. The multiaxial classification approach allows to document separately data from different levels of data collection, such as symptomatological, etiological, psychosocial and family data, as well as personality factors. However, it is always necessary to render any classification empirically valid by verifying it by means of empirically observed data. In this review, some frequently used classifications of schizophrenic psychoses are evaluated regarding their "usefulness". Usefulness of a classification is assumed if its sub-grouping of data on one level of data collection is validated by data from another level, or if there is sufficient evidence that this classification can generate hypotheses which lend themselves to empirical testing. The traditional sub-classification of schizophrenias into hebephrenic, paranoid, catatonic, and simple forms lacks clear rules for allocating patients to one of the sub-groups; moreover, these sub-groups have not proved reliable. Some authors have tried to classify schizophrenic psychoses via the course of the illness. Methodological difficulties are considerable, and hence most of these classification still await validation. On the other hand, the course of premorbid personality development has been shown to be very important for the sub-grouping of schizophrenics: Good vs. poor premorbid adaptation dichotomy has been validated by prognostic and psychophysiological studies, by therapy response and by family data. Any distinction between acute and chronic types is bound to be of rather questionable value. Symptom criteria have also been proposed for differentiating between schizophrenic psychoses. Paranoid vs. nonparanoid dichotomy has been supported by several biochemical, psychophysiological, familial and therapy response studies. There is a great deal of evidence from prognostic and genetic studies that the presence of a valid sub-group of schizophrenic psychoses. Sub-grouping schizophrenics according to narrowly defined symptom criteria such as Schneider's first-rank symptoms and Langfeldt's, Feighner's and Spitzer's research symptom criteria is of limited value for a valid sub-classification. An approach to classification based on the distinction between the predominance of positive vs. negative schizophrenic symptomatology is of heuristic usefulness in that it generates biochemical and pathophysiological hypotheses which can be tested empirically.