An exploration of secondary sex ratios among women diagnosed with anxiety disorders

BACKGROUND Theory suggests that natural selection conserved reactivity in part because highly reactive women spontaneously abort less fit conceptuses, particularly small males. Other literature argues that high reactivity manifests clinically as anxiety disorders. If true, births to women diagnosed with anxiety disorders should exhibit a low secondary sex ratio (i.e. ratio of male to female births). We explored whether births to women diagnosed with anxiety disorders exhibit a lower sex ratio than births to women diagnosed with other psychiatric disorders, or to women without mental health diagnoses. METHODS We performed a case–control comparison of the secondary sex ratios among groups of women categorized by mental health diagnosis using birth records linked to data from California County Mental Health system records. We compared sex ratios among 5994 deliveries to mothers diagnosed with anxiety disorders, 23 443 deliveries to mothers diagnosed with other psychiatric disorders and 1 099 198 ‘comparison’ births. RESULTS Although comparison births exhibited a higher sex ratio than births to women diagnosed with anxiety disorders or with other diagnoses, differences were not statistically significant. Births to African American women diagnosed with anxiety disorders, however, exhibited sex ratios significantly lower than comparison births among African Americans (OR = 0.89, P = 0.038) or births to African American women with other mental health diagnoses (OR = 0.88, P = 0.042). CONCLUSIONS We found that infants born to African American women diagnosed with anxiety disorders exhibited a significantly lower secondary sex ratio than reference groups. We urge confirmatory tests of our findings and discuss implications of the reactivity/anxiety hypothesis for psychiatry, obstetrics and public health.