Elaboration on immigration and risk for schizophrenia

Background: Being a small and culturally different minority, or having a different appearance, has been invoked to account for the increased prevalence of psychotic disorders among immigrants. The majority of the Jewish Israeli population are first- or second-generation immigrants from Europe, North Africa or Asia, and during the late 1980s and 1990s, 885 000 persons immigrated to Israel from the former Soviet Union and 43 000 immigrated from Ethiopia. These Ethiopian immigrants came from a very different culture compared to the rest of the population, and have a distinct appearance. To further understand the association between immigration and schizophrenia, we compared risk for later schizophrenia between adolescents who immigrated from Ethiopia with risk among the other immigrant groups, and with native-born Israelis. Method: Of 661 792 adolescents consecutively screened by the Israeli Draft Board, 557 154 were native-born Israelis and 104 638 were immigrants. Hospitalization for schizophrenia was ascertained using a National Psychiatric Hospitalization Case Registry. All analyses controlled for socio-economic status (SES). Results: Risk for schizophrenia was increased among both first- [hazard ratio (HR) 1.62, 95% confidence interval (CI) 1.18-2.22] and second-generation immigrants [HR 1.41, 95% CI 1.01-1.95 (one immigrant parent) and HR 1.49, 95% CI 1.11-2.0 (two immigrant parents)]. When risk for schizophrenia was calculated for each immigrant group separately, immigrants from Ethiopia were at highest risk of later schizophrenia (HR 2.95, 95% CI 1.88-4.65). Conclusion: This comparison between diverse groups of immigrants supports the notion that immigrants who differ in culture and appearance from the host population are at increased risk for schizophrenia.