Incidence of non-affective psychotic disorders in refugees and peers growing up in Denmark and Sweden: a registry linkage study.

Purpose: Higher rates of non-affective psychotic disorders (NAPD) in minority groups have been reported in many countries. However, few studies have explored how rates differ between refugees and other minority groups and none with an international comparative angle. A comparative perspective makes it possible to relate group differences to aspects national context that underpin the social determinants of disease.

Methods: We compared the incidence of treated NAPD among youth born in or who immigrated to Denmark/Sweden before turning 18. Youth aged 18-35 during 2006-2018 were included (N/N = 1,606,423/2,614,721) and were followed until first NAPD treatment (cases [Denmark/Sweden] = 12,193/9,641), 36 birthday, emigration or death. Incidence rates (IR) and ratios (IRR) comparing refugees, non-refugee migrants, descendants of non-refugee migrants and majority youth were obtained through Poisson regression on data aggregated by country, sex and age, contrasted by sex and country. Complementary analyses on individual-level data adjusting for further socio-demographic factors were conducted in each country separately.

Results: Incidence rates were higher in all groups compared with the majority group (IRR = 1.4-2.9, 95% CI = 1.2-3.1). Relative differences between the three minority groups were smaller (IRR = 0.7-1.0, 95% CI = 0.5-1.2). Although incidence rates were higher in Denmark than Sweden, relative group differences were similar.

Conclusion: Exposures shared between young refugees and other minority groups growing up in Denmark and Sweden may be especially important for their excess risk of NAPD. Further studies should investigate the mechanisms behind the elevated rates in minority groups with special paid attention to factors such as discrimination, social exclusion and acculturation stress.