Increased risk of psychotic disorder among immigrants in Malmö: a 3-year first-contact study.

Background: Previous findings of increased rates of psychotic disorders among immigrants to Sweden are primarily based on hospital samples. The aim of the current study was to compare the risks of first contact for psychotic and schizophrenic disorders among first- and second-generation immigrants to the risks in native 'Swedes'.

Method: During a 3-year period, diagnostic information was collected on all patients with a possible psychotic disorder who made a first-in-lifetime contact with both in-patient and out-patient psychiatric services in Malmö.

Results: First-generation immigrants to Sweden had an increased risk of developing psychotic and schizophrenic disorders compared to Swedes (age- and gender-adjusted relative risk, RR 2.9, 95 % CI 2.0-4.0 and RR 4.0, 95 % CI 1.8-8.6 respectively). Risks for these disorders were not significantly increased in second-generation immigrants. The highest risks of developing psychotic disorder compared to Swedes were found in first-generation immigrants with 'black' (versus 'neither black nor white', or 'white') skin colour (RR 5.8, 95 % CI 2.8-13.4) and birthplace in a developing (versus developed) country (RR 3.3, 95 % CI 2.3-4.8).

Conclusion: The increased risks of psychosis obtained especially in immigrant groups having relatively disadvantaged status in Sweden suggest that psychosocial factors may contribute to the development of psychotic disorders.