Influencia de la gripe materna en la esquizofrenia. Estudio epidemiológico en Galicia (España), de 1999 a 2007

Abstract

The etiology of schizophrenia remains unknown. From the late eighties onwards, a range of theories has been put forward identifying various possible risk factors. One of these was the flu infection (Influenza A virus) during pregnancy, which argues, as a result of an increased incidence being detected in those born in the winter and spring months, that it can affect fetal neurodevelopment. However, the findings which correlate the two are contradictory.

The aim of this study is to link the fluctuations between the distribution of the dates of birth of patients diagnosed with schizophrenia and the distribution of the incidence dates of flu in the general population.

Between 1999 and 2007, a total of 5,911 new diagnoses of schizophrenia were recorded in Galicia, an autonomous region of Spain with a total population of 2,699,499. Furthermore, we have the week-by-week incidence of flu in the general population from 1964 to 2011. On average, the incidence of flu is concentrated in the final 15 weeks and the first 15 weeks of each year, with a higher number of cases registered in the years 1973, 1975 and 2000.

To corroborate the causal hypothesis, the dates of birth of the patients diagnosed with schizophrenia were offset in order to determine the approximate week of conception. Subsequently, this was compared against the 48-weekly distribution of flu, one for each year recorded, by means of the 2 tests. The result of this test rejects the possible causality between the incidence of flu in the mother and the development of schizophrenia in her child.