Competing Definitions of Schizophrenia: What Can Be Learned From Polydiagnostic Studies?

Schizophrenia Bulletin (Impact Factor: 8.45). 10/2007; 33(5):1178-200. DOI: 10.1093/schbul/sbl065
Source: PubMed


The contemporary diagnoses of schizophrenia (sz)-Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition(DSM-IV) and International Classification of Diseases, 10th Revision(ICD-10)-are widely considered as important scientific achievements. However, these algorithms were not a product of explicit conceptual analyses and empirical studies but defined through consensus with the purpose of improving reliability. The validity status of current definitions and of their predecessors remains unclear. The so-called "polydiagnostic approach" applies different definitions of a disorder to the same patient sample in order to compare these definitions on potential validity indicators. We reviewed 92 polydiagnostic sz studies published since the early 1970s. Different sz definitions show a considerable variation concerning frequency, concordance, reliability, outcome, and other validity measures. The DSM-IV and the ICD-10 show moderate reliability but both definitions appear weak in terms of concurrent validity, eg, with respect to an aggregation of a priori important features. The first-rank symptoms of Schneider are not associated with family history of sz or with prediction of poor outcome. The introduction of long duration criteria and exclusion of affective syndromes tend to restrict the diagnosis to chronic stable patients. Patients fulfilling the majority of definitions (core sz patients) do not seem to constitute a strongly valid subgroup but rather a severely ill subgroup. Paradoxically, it seems that a century after the introduction of the sz concept, research is still badly needed, concerning conceptual and construct validity of sz, its essential psychopathological features, and phenotypic boundaries.

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Available from: Josef Parnas
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    • "Nithsdale survey used the ICD 9 criteria to diagnose schizophrenia, while the present study used ICD10. Therefore an important consideration to make is whether any of our findings (prevalence, change in symptoms, social functioning) could be explained as a result of the use of a different classification systems (Jansson and Parnas, 2007). A Danish cross-sectional study, of 155 consecutive 'first-admitted' patients with psychotic illnesses, to an inpatient unit, showed a striking difference in the numbers of patients diagnosed with ICD 9 schizophrenia, compared to ICD 10 (Jansson et al., 2002). "
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    • "). Diagnostic criteria for schizophrenia in DSM–IV–TR consider it as a discrete entity and separate it especially from the affective psychoses (Dutta et al., 2007). As scientific evidence mounts, however, it is doubtful whether these discrete diagnostic groups have discriminant validity (Jansson & Parnas, 2007). Polydiagnostic studies actually do show considerable variation concerning their frequency, concordance, reliability , and outcome when using different sets of diagnostic criteria (Jansson & Parnas, 2007). "
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    • "Second, once a drug is introduced to a clinical population, its efficacy is assessed using traditional clinical end-points, such as clinical rating scales. Their sole dependence on the patients' reports and clinician's observations introduces a subjective element that reduces their sensitivity and precision (Jansson and Parnas, 2007). In addition, these end-points account poorly for the cross-ethnic differences in psychopathology (Brekke and Barrio, 1997), which makes international comparisons difficult. "
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