Leonhard's classification of the chronic schizophrenias
The conceptual development of Leonhard's classification of the chronic schizophrenias is outlined. The recognition within that classification of the importance of the polarity dimension has led to the identification of two distinct populations - atypical nonsystematic and typical systematic schizophrenia - each with a variety of different subtypes. It is hoped that recognition and validation of this group of illnesses which, for three-quarters of a century, have been called 'schizophrenia' will provide a basis for meaningful biological research. Increasing interest in the system has already produced an awareness that future progress in the understanding of mental illness will greatly depend upon re-establishing the central place of psychopathology in psychiatric research.