Comparative genetical analysis: a new tool for validating the schizophrenia subtypes.

350 carefully selected schizophrenic probands and their parents and siblings were diagnosed according to three different clinical classifications, and a multiple-threshold analysis was carried out within the framework of the multifactoral model of inheritance. The results suggest that of the three classification systems, Leonhard's and Sneshnevsky's nosological system delineates relatively homogeneous subtypes from the clinical and genetic point of view, pointing to the promise these nosological systems have for the planning of future research in psychiatric genetics.