This multi-center, randomized, double-blind, placebo-controlled, parallel-group study will
investigate the efficacy and safety of RO4995819 as adjunctive therapy in patients with major
depressive disorder having inadequate response to ongoing antidepressant treatment. Patients
will be randomized to receive once daily doses of 5 mg, 15 or 30 mg of RO4995819 or matching
placebo. The anticipated time on study treatment is 6 weeks.