Does influenza cause schizophrenia? A five year review.

Over the last five years a body of literature has been generated concerning whether or not prenatal exposure to influenza results in an increased risk of developing schizophrenia in the exposed offspring. The studies are reviewed with respect to the traditional epidemiological criteria that help to define causality. There is a modest degree of consistency in support of an association between the 1957 influenza epidemic--and less so, for influenza epidemics in general--and later schizophrenia. Two cohort studies examining the 1957 epidemic do not support an association. The strength and specificity of the association remain weak. The proposed association draws coherence from the neurodevelopmental hypothesis of schizophrenia. Suggestions are made for future research that could add to our understanding of the putative association between influenza and schizophrenia.