Schizophrenia on paternal and maternal sides: an analysis of familial factors.

Slater's model of assessing distribution patterns of ancestral secondary cases in family trees was applied to pedigree data on schizophrenia. Eighteen schizophrenic probands with at least two ill second-degree relatives were available for study. The distribution of unilateral to bilateral pairs of affected relatives did not deviate significantly from that expected in polygenic inheritance. Contrasting pedigrees with family history of chronic schizophrenia with pedigrees loaded with 'soft spectrum' disorders, i.e., borderline schizophrenia, did not alter the consistency of the data with polygenic transmission.