background There are reports of an increased incidence of schizophrenia in certain immigrant groups to the Netherlands.
aim To answer two questions: (1) What is known about the incidence and prevalence?; (2) What is known about aetiology?
method Literature review using Medline and the contents of the 'Tijdschrift voor Psychiatrie' and the 'Maandblad voor de Geestelijke Volksgezondheid' (1985-2001). Also a summary of research conducted abroad is given.
results For subjects of the first generation there is an increased incidence for males and females born in Surinam or the Netherlands Antilles and for Moroccan-born males. There is no excess in Moroccan-born females or in Turkish-born subjects of either sex. For subjects of the second generation an highly increased risk is found for Moroccans and Surinamese. It is unlikely that drug abuse accounts for the findings. Selective migration cannot explain the findings in Surinameseborn immigrants.
conclusions If the frequencies in the countries of origin are not increased, migration is an important risk factor for schizophrenia. The increased figures for both the first and the second generation migrants argue aginst a purely 'biological' aetiology. It is more likely that social factors precipitate the disorder in those who are genetically at risk, but the exact pathogenesis remains to be elucidated.