Sex-specific drivers of non-affective psychotic disorders within migrant groups: a 25-year retrospective cohort study of 2 million migrants

Purpose — Migration is a well-established risk factor for psychotic disorders; however, little is known about factors that may contribute to the risk of psychosis within migrant populations and whether these associations differ by sex. Thus, we sought to identify sex-specific factors that modify the risk of non-affective psychotic disorder (NAPD) among migrant groups.

Methods — We constructed a retrospective cohort of first-generation migrants who arrived in Ontario (Canada) between 1992–2011 (n = 1,964,884). Cohort members were followed in linked health administrative data to identify first-onset cases of NAPD using a validated algorithm. We stratified Poisson regression models by sex to estimate the effects of sociodemographic and migration-related factors on the risk of NAPD among men and women separately.

Results — The incidence of NAPD was higher among migrant men than women (IRR = 1.20, 95% CI: 1.16, 1.23). African origin, family sponsorship, refugee status, and lack of proficiency in the official languages were associated with a higher risk of NAPD among both sexes, with a more pronounced effect in men. North African or Middle Eastern origin and younger age at migration showed specificity of effect for a higher risk of NAPD among men only. Among adult migrants (age 19 +), marital and common-law relationships exerted a greater protective effect among men, whereas higher education was protective among men only.

Conclusion — We identified sex-based differences in factors that modify psychosis risk among migrant groups. These sex-specific factors may help explain variations in NAPD incidence and define high-risk subgroups for targeted prevention and early intervention efforts.