Bilateral inheritance as evidence for polygenicity in functional psychoses

Among 1,678 functional psychoses followed up, 35 had parents, uncles, aunts or grandparents with 2 or more cases diagnosed as schizophrenic psychoses, or 2 or more secondary relatives diagnosed as non-schizophrenic psychoses. Comparisons of unilateral and bilateral inheritance suggest that the schizophrenic and endogenous affective psychoses have polygenic transmission, while this is not the case for reactive psychoses.