Risk of schizophrenia in second-generation immigrants: a Danish population-based cohort study.
BACKGROUND
Urban birth, a risk factor for schizophrenia, is more frequent among second-generation immigrants. The aim of the current study was to determine whether the increased risk for schizophrenia found in second-generation immigrants is explained by the degree of urbanization of birthplace and/or factors related to parentage, such as geographic origin or history of residence abroad during upbringing.


METHODS
Using data from the Danish Civil Registration System (CRS), we established a population-based cohort of 2.0 million Danes (persons born in Denmark). Schizophrenia in cohort members was identified by cross-linkage with the Danish Psychiatric Central Register.


RESULTS
The relative risk of developing schizophrenia was 1.93 [95% confidence interval (CI) 1.79-2.08] and 2.96 (95% CI 2.49-3.51) among persons with one or both parents foreign-born respectively compared to native Danes. Adjustment for urbanization of birthplace and parental characteristics reduced these risks slightly. However, urbanization had a lesser effect in second-generation immigrants than in Danes. History of residence abroad was a risk factor for schizophrenia, regardless of whether parents were foreign-born or native Danes.


CONCLUSIONS
The increased risk found in second-generation immigrants cannot be explained by urbanization or parental characteristics pertaining to age, mental illness, geographic origin or residence abroad during a child's upbringing.
Cantor-Graae
Elizabeth
E
Department of Health Sciences, Lund University, University Hospital Malmö, Malmö, Sweden. elizabeth.cantor-graae@med.lu.se
Pedersen
Carsten B
CB
D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D004641:Emigration and Immigration / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D011159:Population Surveillance / Q000379:methods; D012307:Risk Factors; D012559:Schizophrenia / Q000208:ethnology* / Q000235:genetics*; D014505:Urban Population / Q000706:statistics & numerical data