Major depressive disorders in young immigrants: A cohort study from primary healthcare settings in Sweden.

Aims: Previous studies on major depressive disorder (MDD) among immigrants have reported mixed results. Using data from primary healthcare settings in Sweden, we compared the incidence of MDD among first- and second-generation immigrants aged 15-39 years with natives.

Methods: This was a retrospective nationwide open cohort study. Eligible individuals were born 1965-1983, aged 15-39 years at baseline, and resided in Sweden for at least one year during the study period 2000-2015. We identified MDD cases through the Primary Care Registry (PCR). The follow-up for each individual started when they met the inclusion criteria and were registered in the PCR and ended at MDD diagnosis, death, emigration, moving to a county without PCR coverage, or the end of the study period, whichever came first. Results: The final sample included 1,341,676 natives and 785,860 immigrants. The MDD incidence rate per 1000 person-years ranged from 6.1 (95% confidence intervals: 6.1, 6.2) to 16.6 (95% confidence intervals: 16.2, 17.0) in native males and second-generation female immigrants with a foreign-born father, respectively. After adjusting for income, the MDD risk did not differ substantially between first-generation male and female immigrants and natives. However, male and female second-generation immigrants had a 16-29% higher adjusted risk of MDD than natives.

Conclusions: This cohort study using primary healthcare data in Sweden, albeit incomplete, indicated that second-generation immigrants seem to be at a particularly high risk of MDDs. The underlying mechanisms need further investigation.