Sex concordance for schizophrenia in proband-relative pairs.

Some hypotheses about the cause of schizophrenia are based on the puzzling tendency for mental illness to affect the same sex when two close relatives become psychiatrically ill. Sex-concordance rates were examined in 71 schizophrenic probands, who had at least one first-degree relative suffering from the same disorder, in order to test this tendency in a population of recently admitted patients. No unusual concordance rates were found when unaffected sibs were taken into account and relatives were stratified to take account of possible confounding factors. It would seem premature to construct hypotheses about the aetiology of schizophrenia based on evidence of this type.