IFNA1 and major depressive disorder: The adjusted hazard ratios for recurrent depressive disorder were 13.5 (95% CI, 9.9–18.3) in the IFN-α-treated cohort and 22.2 (95% CI, 11.2–44.2) in the matched cohort for IFN-α-induced depression patients after adjusting for age, sex, income, urbanization and comorbid diseases.