A contribution to the validity of Leonhard's classification of endogenous psychoses.

The author made a clinical-genetical study of the schizophrenias and cycloid (schizoaffective) psychoses following the Leonhardian classification, using the traditional pedigree analysis and multiple threshold method. According to the latter method--on the basis of phenotypical correlations--the systematic schizophrenias could be clearly distinguished from the cycloid psychoses, while the non-systematic category presumably occupies a genetical position between the two former categories.