Association of neighborhood migrant density and subsequent risk of non-affective psychosis: a national, longitudinal cohort study

Importance: Elevated risk of psychotic disorders in migrant groups is a pressing public mental health priority. Understanding the role of neighborhood factors, like migrant density, may further our understanding of the aetiology of psychotic disorders and highlight potential areas for public health intervention. Objective: To investigate whether migrants and their children living in areas of high own-region migrant density have lower risk of non-affective psychosis and consider whether generation status or visible minority status affect this relationship. Design: Cohort study using Swedish register data of all migrants and their children living in Sweden after 15 years old, born between 1982 and 1996. Setting: Nationwide study of all small area neighborhoods in Sweden. Participants: 468,223 migrants and children of migrants. Individuals were followed from age 15 or date of migration following their 15th birthday until a diagnosis of non-affective psychosis, emigration, death, or end of December 2016. Exposures: Neighborhood own-region migrant density and generation-specific own-region migrant density at cohort entry.Outcomes: ICD-10 diagnosis of non-affective psychosis (F20-29) as recorded in the National Patient Register between 1997 and 2016. Results: Overall, a 5% decrease in own-region migrant density was associated with an increased risk of non-affective psychosis (HR: 1.05; 95%CI 1.03-1.06), with similar effects for migrants (HR: 1.05; 95%CI 1.02-1.07) and children of migrants (HR: 1.03; 95%CI 1.01-1.06). A stronger effect was observed in probable visible minority migrants than non-visible minority migrants (HR: 1.07; 95%CI 1.04-1.11; HR: 0.99; 95%CI 0.94-1.04, respectively), with similar patterns for children of migrants. Conclusions and relevance: This study provides further evidence for the importance of the neighborhood environment in psychosis risk among migrants and their children. Stronger protective effects of migrant density, particularly for first generation migrants and those likely to be of visible minority status suggest this health inequality may arise be socially constructed.