Objective: Selective serotonin reuptake inhibitors (SSRIs) are the cornerstone of treatment of major depressive disorder (MDD). However, non-response is common, often necessitating combination strategies. The present study assessed the efficacy of vortioxetine as an add-on therapy in patients with SSRI-resistant MDD.Methods: The charts of 36 adult outpatients with DSM-IV-TR MDD who had not achieved a response after at least 8 weeks of treatment with an SSRI were reviewed retrospectively. Subjects were treated with vortioxetine (5-20 mg/day) for 8 weeks added to the current SSRI. The main outcome measures were change from baseline in total Hamilton Scale for Depression (HAM-D) score and the rate of response (a 50% or greater reduction in HAM...