Genetic models of sex effect in unipolar affective illness

Family study data on unipolar affective illness are analyzed by multiple threshold models of inheritance that incorporate sex effect. In these models males and females share a common genetic-environmental liability, but the less prevalent sex, i.e., males, has a higher genetic threshold for the disorder. Neither single major locus (SML) nor multifactorial-polygenic (MFP) transmission can account for the sex differences in the morbid risk for unipolar disorder. The implications for genetic research in affective disorders are discussed.