Social adversity contributes to high morbidity in psychoses in immigrants – a national cohort study in two generations of Swedish residents

Background. Recent reports have indicated that immigrants have an elevated risk of schizophrenia as well as an increasing tendency for social exclusion. The aim of this study was to compare rates of schizophrenia and other psychoses in immigrants and their children of different ethnic groups with the majority population in Sweden in relation to social adversity.

Method. The study population consists of a national cohort of 1·47 million adults (born 1929–1965) and 1·16 million children and youth (born 1968–1979) in family households from the national census of 1985. Multivariate Cox regression analyses was used to study hospital discharge data during 1991–2000 in relation to socio-economic household indicators from 1985 and 1990 (single adult household, adults having received social welfare, parental unemployment, urban residency, housing and socio-economic status).

Results. First as well as second generation immigrants had higher age and sex adjusted risk ratios for schizophrenia as well as for other psychoses (RRs 1·4–3·1 and 1·0–2·0 respectively) compared with the Swedish majority population. These risk ratios decreased considerably after adjusting for socio-economic indicators, for all groups, but particularly for the non-European immigrants. However, an elevated risk still remained in the Finnish and Eastern and Southern European study groups.

Conclusions. A higher risk of schizophrenia and psychoses was found in two generations of immigrants of diverse ethnicity. The results indicate that social adversity contributes to the higher risk.