Evidence for a gender bias in epidemiological studies of schizophrenia.

A higher lifetime morbidity risk for schizophrenia in males has been observed by several investigators. Studies controlled for errors in patient selection and other sources of artefacts, however, find an equal risk in both sexes. In order to detect the causes for the underrepresentation of women in many studies, sample composition of multicentre WHO studies was analysed. Severity of symptoms was not found to be responsible for imbalances in the male/female ratios, but cultural influences and design characteristics were: due to the scarcity of psychiatric facilities, women are less likely to receive adequate treatment in most of the developing countries investigated, since they are kept longer at home and seen by traditional healers in some cultures. Also, studies with an upper age limit of 44 years (according to DSM-III) exclude a greater proportion of female than male schizophrenic patients, and there is some evidence that schizophrenia is more often underdiagnosed in women than in men at least in some countries. Implications for future research on gender differences in schizophrenia are discussed.