No. 25: Jan-Feb 1983
Several scientists have published data that suggest that schizophrenics are more likely to be born in the winter months. The data have been subjected to much criticism. In this paper, the authors were careful to avoid previous errors in data collecting and analysis. From the Abstract:
"We studied the birth months of 3,556 schizophrenics at a Minnesota Veteran's Administration hospital before and after instituting corrections for year-to-year across-month variations in birthrates in our expected values and the age-prevalence bias toward the January-March seasonality effect described in some earlier studies. Finally, we reanalyzed our data on a subset of patients in whom the ageincidence effect should be minimal. Even after these corrections the results supported the contention that the winter birthrate for schizophrenics is excessive, at least in severe climates."
(Watson, Charles G., et al; "Season of Birth and Schizophrenia: A Response to the Lewis and Griffin Critique," Journal of Abnormal Psychology, 91:120, 1982.)
Comment. What could possibly cause this seasonal effect, assuming it withstands scrutiny?