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Author for correspondence: Jean-Paul Selten, E-mail: [email protected] and [email protected]
Introduction
Migrants face the difficult task of settling into the society of a new country. It is not surprising, therefore, that a recent meta-analysis found migrants to be at increased risk of developing mood disorders (pooled relative risk, RR, 1.25, 95% CI 1.11–1.41) (Mindlis and Boffetta, 2017). Meta-analytic evidence, however, suggests that migrants and their children are at an even higher risk for schizophrenia or other non-affective psychotic disorders (NAPDs), with RRs exceeding 2.0 (Cantor-Graae and Selten, 2005; Bourque et al., 2011).
As the last meta-analysis included studies up to 2008, there is a need for an up-to-date, comprehensive meta-analysis that estimates not only the risk of NAPD, but also that of affective psychotic disorder (APD), and that adjusts for socioeconomic status (SES) in the country of destination. Two competing theories have been proposed to explain the low SES of individuals who develop a psychotic disorder (PD): social causation (stress) and social selection (downward mobility of the genetically predisposed). Since there is little evidence of an association between parental SES and risk of psychosis, the mechanism of social selection may be more important than that of social causation (Dohrenwend et al., 1992; Kwok, 2014). Indeed, research has shown that a large part of this downward mobility occurs before the development of psychosis, in that many patients with psychosis fail to reach their expected educational level (Kendler et al., 2016). However, since a role for social causation cannot be entirely excluded, it is important to adjust any effect of migration for SES.
A previous meta-analysis reported that the risk of NAPD did not differ significantly between first- and second-generation migrants (Bourque et al., 2011), which suggests that ethnic minority status rather than migration is an important factor in the development of psychosis. In order to investigate this and other potential factors, we performed a meta-analysis of incidence studies (i) to estimate the pooled RR (v. the reference population) of developing APD, NAPD, or any of these disorders, among international migrants and their children; (ii) to adjust these results for SES; and (iii) to examine sources of heterogeneity with reference to the RR of NAPD, such as generational status (first or second),...