Incidence of psychotic disorders in immigrant groups to the Netherlands

TLDR

Previous studies on schizophrenia incidence in Dutch immigrants relied on hospital data, and rapid westernisation may precipitate the disorder in genetically susceptible individuals. The study compares psychotic disorder incidence in immigrant groups to native Dutch. A two‑year first‑contact incidence study was conducted in The Hague. Schizophrenia incidence was markedly higher among Moroccan, Surinamese, Netherlands Antilles, and other non‑Western immigrants, especially in second‑generation Moroccans and Surinamese, while Turkish and Western immigrants showed no significant rise, indicating that increased incidence occurs in some but not all immigrant groups in the Netherlands.

Abstract

Background Previous reports on the incidence of schizophrenia in immigrant groups to The Netherlands were based on hospital data. Aims To compare the incidence of psychotic disorders in the immigrant groups to that in natives. Method Two-year first-contact incidence study in The Hague. Results The risks of schizophrenia, schizophreniform or schizoaffective disorder (DSM–IV criteria) were increased for subjects born in Morocco (gender and age-adjusted relative risk=4.5; 95% CI 1.4–8.5), Surinam (relative risk=3.2; 1.8–5.7), The Netherlands Antilles (relative risk=2.9; 0.9–9.5) and other non-Western countries (relative risk=2.4; 1.3–4.7). This risk was also increased for Moroccans (relative risk=8.0; 2.6–24.5) and Surinamese (relative risk=5.5; 2.5–11.9) of the second generation. The risks for Turkish immigrants, first or second generation, and for immigrants from Western countries were not significantly increased. Conclusions This study indicates that the incidence of schizophrenia is increased in several, but not all, immigrant groups to The Netherlands. It is possible that factors associated with a process of rapid westernisation precipitate schizophrenia in people who are genetically at risk.