A shifting seasonality of schizophrenic births.

In view of recent findings in Japan, and in England and Wales, data on schizophrenic births in the United States were reexamined to see if seasonal shifts had occurred. In Missouri a progressive shift from February to April and May was noted between 1921 and 1930 and between 1941 and 1950. In five New England states there was no shift over the same period. Data were then obtained to compare the Missouri shift with two hypotheses previously put forward to explain schizophrenic birth seasonality: (1) that it is related to the seasonality of general births, and (2) that it is related to seasonal temperature variation. Neither hypothesis was supported by the data.