In-utero determinants of adult depression: evidence from the 1918 flu pandemic.

Social scientists have dealt only glancing with potential in-utero determinants of mental health. This study looks at the enduring consequences of gestational exposure to the 1918 flu pandemic for adult depression. It does so using data collected in the first wave of the National Health and Nutrition Examination Survey (1971-1975), corresponding to when those exposed in-utero were in their early to mid-50s. The results indicate very strong effects of in-utero exposure on depression. These effects are only found, however, among men. The effects are sufficiently large to eliminate sex differences in major depression within a cohort: among those born in 1919, the prevalence of major depression is about 1 in 5 for both men and women. Additional analyses further clarify the relationship, showing effects of in-utero exposure across the full spectrum and syndrome of depressive symptoms. In addition, the effects are stronger for symptoms related to depression than for symptoms related to schizophrenia. Additional analyses show that the effect of exposure is reduced somewhat when adjusting for later socioeconomic disadvantages. In addition, the effect is reduced when controlling for broader dimensions of physical health. Yet neither of these relationships explains the effects of exposure altogether.