Where have all the women gone?. Participant gender in epidemiological and non-epidemiological research of schizophrenia

Though archival literature states that schizophrenia occurs equally in males and in females, recent epidemiological studies report higher incidence of schizophrenia in men than in women. Moreover, there is longstanding evidence that women may be under-represented in non-epidemiological research literature. Our first goal was to quantify gender ratios in non-epidemiological research published in 2006. Secondly, we sought to investigate which factors contribute to high numbers of men in research studies. Our final goal was to compare gender ratios in non-epidemiological schizophrenia research to reported incidence rates. In a recent meta-analysis of incidence, there were 1.4 males for each female with schizophrenia. In non-epidemiological studies of the schizophrenia patients, there was an average of 1.94 men for every woman. Although the degree to which men outnumbered women varied according to study type and region of study, research studies included more men than women across all investigated variables. Either the incidence rates are higher for men than has previously been reported or women are less visible in research settings than in the greater community. Importantly, the discrepancy between gender ratios in epidemiological and non-epidemiological research is consistent. However, specific, identifiable factors are present when male participants are greatest, suggesting that many research environments yield a higher number of men. Thus much of our understanding of the illness and its treatment is based on research conducted disproportionately with men.