Concordance for gender in sib pairs affected with schizophrenia and related disorders

An excess concordance by sex among siblings affected with schizophrenia has been proposed by some previous and recent investigators. However, this hypothesis has not been supported by some recent studies having complete ascertainment of probands and relatives. The present report is based on sibships with multiple affected members derived from a family study of systematically recruited inpatients (146 probands with schizophrenia and 132 probands with other psychotic disorders). Evidence for an excess concordance rate for gender among proband-sibling pairs with both members affected is suggested under a broad definition of illness.