Background: Migration is an established risk factor for developing a psychotic disorder in countries with a long history of migration. Less is known for countries with only a recent history of migration. This study aimed to determine the risk for developing a psychotic disorder in migrants to the Republic of Ireland.
Methods: We included all presentations of first-episode psychosis over 8.5 years to the DETECT Early Intervention for psychosis service in the Republic of Ireland (573 individuals aged 18-65, of whom 22% were first-generation migrants). Psychotic disorder diagnosis relied on SCID. The at-risk population was calculated using census data, and negative binomial regression was used to estimate incidence rate ratios.
Results: The annual crude incidence rate for a first-episode psychotic disorder in the total cohort was 25.62 per 100000 population at risk. Migrants from Africa had a nearly twofold increased risk for developing a psychotic disorder compared to those born in the Republic of Ireland (IRR = 1.83, 95% CI 1.11-3.02, p = 0.02). In contrast, migrants from certain Asian countries had a reduced risk, specifically those from China, India, Philippines, Pakistan, Malaysia, Bangladesh and Hong Kong (aIRR = 0.36, 95% CI 0.16-0.81, p = 0.01).
Conclusions: Further research into the reasons for this inflated risk in specific migrant groups could produce insights into the aetiology of psychotic disorders. This information should also be used, alongside other data on environmental risk factors that can be determined from census data, to predict the incidence of psychotic disorders and thereby resource services appropriately.
Keywords: Schizophrenia; incidence; migration; psychosis.