Objective To examine prenatal and perinatal risk factors for subsequent development of schizophrenia and affective and reactive psychosis.

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We examined the relationship between the dates of births of schizophrenic patients admitted to hospitals for the first time in England and Wales between 1970 and 1979, and the occurrence of influenza epidemics between 1939 and 1960. Our results indicate that exposure to influenza epidemics between the third and seventh month of gestation is associated with schizophrenia in adult life. The hypothesis that maternal viral infection is an important cause of schizophrenia can explain many aspects of the enigmatic epidemiology of the condition.

SynopsisAge and sex-adjusted first admission rates for operationally-defined schizophrenia and other non-affective psychosis in different ethnic groups were calculated over the period 1988–1992 in a defined catchment area in South London. Standardized rates for schizophrenia, corrected for age- and gender-related under-reporting in the 1991 census and a 20% underestimate of the size of the ethnic minority populations in the area, were not only higher in the Afro-Caribbean group (SMR: 3·1; 95% Cl: 2·0–4·7), but also in the African group (SMR: 4·2; 95% Cl: 2·8–6·2). It was further found that higher rates were not specific to schizophrenia. These findings suggest that some common factor associated with ethnic minority membership is important in producing an excess of psychotic illness.

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