Objective: We aimed to identify those patients with hepatitis C virus who benefit most from prophylactic treatment with selective serotonin reuptake inhibitors (SSRIs) during antiviral therapy. Method: We performed post hoc analyses on a prospective randomized controlled trial (n = 79) of escitalopram versus placebo during antiviral therapy with pegylated interferon and ribavirin, conducted between August 2005 and June 2008. Our primary outcome measure was the association of baseline characteristics with the development of depression and/or depressive symptoms. Further, we studied effects of prophylactic escitalopram on depressive symptoms. Presence of a major depression was diagnosed using Mini-International Neuropsychiatric Interview (MINI), a short, structured interview used to diagnose DSM-IVTR and ICD-10 disorders. Depressive symptoms were monitored during treatment by using the depression scale of Symptom Checklist-90 (SCL-90), Montgomery-Asberg Depression Rating Scale (MADRS), and Beck Depression Inventory (BDI) at baseline and weeks 4, 12, and 24 of antiviral therapy. Results: Depression occurred in 14 patients receiving placebo and in 5 patients receiving escitalopram (Pearson chi(2), P = .01). Combination of history of depression and intravenous drug use was associated with depression (odds ratio = 12.60; 95% CI, 2.47-64.34; P < .01). Moreover, treatment with selective serotonin reuptake inhibitor compared to placebo was associated with a significant reduction in estimated mean depressive symptoms measured by SCL-90 (P = .03) and BDI (P = .048), but not with MADRS (P = .64). Conclusions: Patients infected by hepatitis C virus with a history of depression and intravenous drug use carry the highest risk to develop interferon-induced depression. In this subset of patients, prophylaxis with escitalopram results in the most substantial decrease of interferon-induced depressive symptoms on the SCL-90 depression scale and the BDI. (C) Copyright 2014 Physicians Postgraduate Press, Inc.