Is schizophrenia what it was? A re-analysis of Kraepelin's and Bleuler's population

It has been noted that the term "schizophrenia" is now applied to a group in many ways dissimilar to Emil Kraepelin's cases of dementia praecox and Eugene Bleuler's of schizophrenia. No detailed explanation has been offered for the difference. This article offers evidence that Kraepelin's and Bleuler's concepts were derived from a population largely suffering from organic disorders including the Parkinsonian sequelae of encephalitis lethargica; it describes the conceptual confusion which followed the introduction of the concept of post-encephalitic Parkinsonism and discusses some implications for the modern concept of schizophrenia. It is suggested that the differences between earlier and later groups of schizophrenics may be accounted for by the decline in prevalence of post-encephalitic Parkinsonism and of the neurological and behavioral sequelae of other diseases, and by the parallel unsystematic development of the concept of schizophrenia.