The impact of diagnostic criteria on the prevalence of schizophrenic subtypes

The distribution of schizophrenic subtypes shows a high range of cross-cultural and historical variations. Our study aimed to investigate the effect of different diagnostic criteria on the prevalence of schizophrenic subtypes. A sample of 220 consecutively admitted schizophrenic patients from 3 different psychiatric institutions was classified according to Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, International Statistical Classification of Diseases, 10th Revision, and Bleuler's and Leonhard's criteria. Especially, the frequency of catatonic (10%-22%) and hebephrenic (5%-20%) subtypes of schizophrenia varied within a broad range depending on the diagnostic system applied. The comparison of International Statistical Classification of Diseases, 10th Revision and Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition with “classical” criteria (Bleuler, Leonhard) for the different schizophrenic subtypes showed a reduction of typical symptoms and the introduction of criteria of prominence during the last century. These changes caused 2 trajectories (“paranoidization” and “shift into residual categories”) explaining these cross-sectional variations.