Associations between mental illness, TB risk and migrant status.

Background: TB and mental illnesses are public health priorities that often co-exist, with migrants in high-income countries being at risk for both conditions. This study investigates whether mental illness influences TB risk and examines the impact of migration status.

Methods: A nationwide prospective cohort study was conducted in Denmark from 1994-2015, involving migrants matched 1:6 to Danish-born individuals. Cox regression models, adjusted for age, sex and migrant status, were used to assess the effect of mental disorders on TB risk.

Results: Both migrants and non-migrants with mental disorders showed elevated TB incidence (n = 1,189,273). After adjusting for age and sex, the hazard ratio (HR) for TB in those with any mental disorder was 3.62 (95% CI 2.99-4.39, P < 0.001) compared to those without mental disorders. The effect was more substantial in Danish-born individuals (HR 15.51, 95% CI 12.05-19.95, P < 0.001) than in migrants (HR 1.37, 95% CI 0.99-1.90, P = 0.055). Sub-analyses highlighted a significant effect of substance use (HR 5.49, 95% CI 4.46-6.76, P < 0.001) and psychosis (HR 4.19, 95% CI 1.74-10.08, P = 0.001) and borderline significance for affective/anxiety/stress-related disorders (HR 1.64, 95% CI 0.98-2.73, P = 0.058) on TB risk.

Conclusions: People with mental illnesses, particularly psychotic and substance use disorders, have increased TB incidence and represent a high-risk population for targeted screening and treatment. TB programmes should integrate holistic mental health care.