Migration as a risk factor for schizophrenia: A Danish population-based cohort study

Abstract

Background: A growing body of evidence suggests that migration is a risk factor for the development of schizophrenia, although the putative mechanism remains obscure. Aims: To examine immigrant background and history of foreign residence as risk factors for schizophrenia. Method: Using data from the Danish Civil Registration System, we established a population-based cohort of 2.14 million persons resident in Denmark by their fifteenth birthday. Schizophrenia in cohort members and parental psychiatric disorder were identified by cross-linkage with the Danish Psychiatric Case Register. Results: The relative risk of developing schizophrenia was 2.45 (95% CI 2.25-2.67) and 1.92 (95% CI 1.74-2.12) among first- and second-generation immigrants respectively, and 1.60 (95% CI 1.25-2.05) among Danes with a history of foreign residence. Conclusions: Migration confers an increased risk for schizophrenia that is not solely attributable to selection factors and may also be independent of foreign birth.