IFNA1 and major depressive disorder: Therapeutic administration of IFN-α leads to depression in up to 50% of patients, and up to 30% of patients develop IFN-α-induced depression (a major depressive episode according to Diagnostic and Statistical Manual of Mental Disorders, 4th edn diagnostic criteria) within the first 3 months.8, 9, 10 In addition, the clinical benefit of IFN-α is compromised by its common and severe neuropsychiatric adverse effects.