Vortioxetine (Lu AA21004) is an antidepressant with a mechanism of action thought to be related to a combination of 2 pharmacologic actions: direct modulation of several receptors and inhibition of the serotonin transporter.To evaluate the efficacy of vortioxetine 10 and 20 mg once daily in outpatients with major depressive disorder.This 8-week, multicenter, randomized, double-blind, placebo-controlled, parallel-group study was conducted from July 2010 to January 2012 among adults with a primary diagnosis of recurrent major depressive disorder (DSM-IV-TR).Eligible subjects were randomized in 1:1:1 ratio to 1 of 3 treatment arms: vortioxetine 10 mg, vortioxetine 20 mg, or placebo once daily for 8 weeks.