Susser and Lin1 report the remarkable finding of an increased risk for hospitalized schizophrenia in women whose mothers were among the population exposed to severe famine during the Dutch Hunger Winter of 1944 through 1945 and who were members of a risk set alive at 19 years of age. The authors' broad consideration of the limitations of their analysis is to be commended, and the result is discussed in the context of other lines of evidence in favor of antenatal risk factors for schizophrenia, albeit at various and contradictory periods of gestation. However, I am curious as to one point of detail and take issue with their conclusion regarding gender differences in the increased relative risk.
It is unclear whether the numerator for exposed and unexposed groups consists of true incident cases of schizophrenia, ie, first hospital admissions, or the total number of admissions for schizophrenia, including readmissions, appearing in
Jones P. Schizophrenia After Prenatal Exposure to the Dutch Hunger Winter of 1944-1945. Arch Gen Psychiatry. 1994;51(4):333. doi:10.1001/archpsyc.1994.03950040077010