In this 8-week , multicentre , double-blind , placebo-controlled , parallel-group , phase 3 study , patients with a primary GAD diagnosis were randomised to receive placebo ( n = 157 ) , vortioxetine 2.5 mg , vortioxetine 5 mg , vortioxetine 10 mg or duloxetine 60 mg once daily ( n = 156 each ) .