No significant association between prenatal exposure poliovirus epidemics and psychosis.

Objective: To examine the association between prenatal exposure to poliovirus infection and later development of schizophrenia or affective psychosis in a Southern Hemisphere psychiatric register.

Methods: We calculated rates of poliomyelitis cases per 10 000 background population and rates for schizophrenia(n = 6078) and affective psychosis (n = 3707)per 10 000 births for the period 1930-1964. Empirically weighted regression was used to measure the association between a given psychosis birth-rate and a poliomyelitis epidemic during gestation.

Results: There was no statistically significant association between exposure to a poliomyelitis epidemic during gestation and subsequent development of schizophrenia or affective psychosis.

Conclusions: The lack of a consistent statistically significant association between poliovirus epidemics and schizophrenia suggests that either poliovirus may have a small effect which is only detectable with large data-sets and/or the effect may be modified by location. Further investigation of such inconsistencies may help elucidate candidate risk-modifying factors for schizophrenia.