Does prenatal influenza divert susceptible females from later affective psychosis to schizophrenia?

We examined the relationship between influenza epidemics and the number of schizophrenic and affective psychotic individuals born each month between 1938 and 1965 in England and Wales. Increased death rates from influenza were followed 5 months later by a significant increase in schizophrenic births and a concurrent fall in the number of births of affective psychotic individuals. When the sexes were examined separately, both the positive effect of influenza on schizophrenic births and its negative effect on affective psychotic births were evident for females but not for males. Furthermore, during February to June in high influenza years, there was an inverse relationship between the number of female schizophrenic and affective psychotic births. The explanation for these surprising findings may be that prenatal exposure to influenza impairs the neurodevelopment of some females with a predisposition to affective psychosis, in such a way that their later illness shows schizophrenic rather than affective features.