Abstract
We assessed whether the risk of various psychotic disorders and non-psychotic bipolar disorder (including mania) varied by migrant status, a region of origin, or age-at-migration, hypothesizing that risk would only be elevated for psychotic disorders. We established a prospective cohort of 1 796 257 Swedish residents born between 1982 and 1996, followed from their 15th birthday, or immigration to Sweden after age 15, until diagnosis, emigration, death, or end of 2011. Cox proportional hazards models were used to model hazard ratios by migration-related factors, adjusted for covariates. All psychotic disorders were elevated among migrants and their children compared with Swedish-born individuals, including schizophrenia and schizoaffective disorder (adjusted hazard ratio [aHR]migrants: 2.20, 95% CI 1.96-2.47; aHRchildren : 2.00, 95% CI 1.79-2.25), affective psychotic disorders (aHRmigrant1.42, 95% CI 1.25-1.63; aHRchildren: 1.22 95% CI 1.07-1.40), and other non-affective psychotic disorders (aHRmigrant: 1.97, 95% CI 1.81-2.14; aHRchildren: 1.68, 95% CI 1.54-1.83). For all psychotic disorders, risks were generally highest in migrants from Africa (i.e. aHRschizophrenia: 5.24, 95% CI 4.26-6.45) and elevated at most ages-of-migration. By contrast, risk of non-psychotic bipolar disorders was lower for migrants (aHR: 0.58, 95% CI 0.52-0.64) overall, and across all ages-of-migration except infancy (aHR: 1.20; 95% CI 1.01-1.42), while risk for their children was similar to the Swedish-born population (aHR: 1.00, 95% CI 0.93-1.08). Increased risk of psychiatric disorders associated with migration and minority status may be specific to psychotic disorders, with exact risk dependent on the region of origin.
Highlights
We assessed whether the risk of various psychotic disorders and non-psychotic bipolar disorder varied by migrant status, a region of origin, or age-atmigration, hypothesizing that risk would only be elevated for psychotic disorders
A Dutch study found the highest risk of psychotic disorders with infant migration (Veling et al, 2011), while a more recent British study found risk peaked with early childhood migration (Kirkbride et al, 2017b)
We studied four psychiatric outcomes: schizophrenia or schizoaffective disorder (F20.X, F25.X); affective psychotic disorders (F30.2, F31.2, F31.5, F32.3, F33.3), other non-affective psychotic disorders (F21.X-F24.X, F28.X- F29.X) and; bipolar disorder or manic symptoms without confirmed psychotic symptoms (F30.1, F30.8, F30.9, F31.0–31.1, F31.3– 31.4, F31.6–31.9)
Summary
We assessed whether the risk of various psychotic disorders and non-psychotic bipolar disorder (including mania) varied by migrant status, a region of origin, or age-atmigration, hypothesizing that risk would only be elevated for psychotic disorders. Risk of non-psychotic bipolar disorders was lower for migrants (aHR: 0.58, 95% CI 0.52–0.64) overall, and across all ages-of-migration except infancy (aHR: 1.20; 95% CI 1.01–1.42), while risk for their children was similar to the Swedish-born population (aHR: 1.00, 95% CI 0.93–1.08). By contrast, elevated rates have not been consistently shown for bipolar disorder among migrants (Swinnen and Selten, 2007) or their children (Cantor-Graae and Pedersen, 2013; Pignon et al, 2017). Previous studies have rarely distinguished between bipolar disorders presenting with and without psychotic features When restricted to those with psychosis, there is some evidence of higher rates of bipolar disorder in migrants and their children (Lloyd et al, 2005). No study to date has examined age-at-migration in relation to bipolar disorders, with or without psychosis
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