Age-at-migration, ethnicity and psychosis risk: findings from the EU-GEI case-control study

Background: Several studies have highlighted increased psychosis risk in migrant and minority ethnic populations. Migration before age 18 appears to increase risk, but further evidence is required. We investigated this issue in a European case-control study. We hypothesized that migration during two key socio-developmental periods, childhood and adolescence, would be most strongly associated with increased odds of psychosis, and that this would be more pronounced for racialised minorities. Method: We used data from five countries in the EUropean network of national schizophrenia networks studying Gene-Environment Interactions EU-GEI study. We examined the association between migration in infancy (0-4 years), childhood (5-10 years), adolescence (11-17 years) or adulthood (18+ years) and first episode psychotic disorder. We fitted unadjusted and adjusted logistic regression models to estimate odds ratios OR and 95% confidence intervals 95%CI for associations between age-at-migration and psychosis. In stratified models, we also examined whether these associations varied by ethnicity.Results: The sample consisted of 937 cases and 1,195 controls. Migration at all ages, including infancy (OR: 2.03, 95%CI: 1.01-4.10), childhood (OR: 2.07, 95%CI: 1.04-4.14), adolescence (OR: 3.26, 95%CI: 1.89-5.63) and adulthood (OR: 1.71, 95%CI: 1.21-2.41), was associated with increased odds of psychosis compared with the white majority non-migrant group, after adjustment for all confounders except ethnoracial identity. After additional adjustment for ethnoracial identity, only migration during adolescence remained associated with psychosis (OR 1.94, 95%CI: 1.11-3.36). In stratified analyses, migration during adolescence was associated with increased odds of psychosis in Black (OR: 6.52, 95%CI: 3.00-14.20) and North African (OR: 16.43, 95%CI: 1.88-143.51) groups.Conclusion: Migration during adolescence increased psychosis risk, particularly in racially minoritised young people. This suggests that development of interventions for minoritised young migrants that alleviate stressors associated with migration and acculturation are warranted.