In previous studies, patients who developed symptoms early in the course of IFN-α had predominantly neurovegetative and somatic symptoms and were less responsive to antidepressant treatment.23 Almost half of IFN-α-induced depression occurred in the first 2 months of our study, and there was no difference in the recurrence risk among the IFN-α-induced depression onset categories of less than 45 days, 46–90 days and more than 90 days. This evidence concerns the gene IFNA1 and depressive disorder.