ARTDeCo Study: A Study of RO4995819 in Patients With Major Depressive Disorder And Inadequate Response to Ongoing Antidepressant Treatment

Inclusion Criteria: * Adult patients, 18-65 years of age * Major depression disorder without psychotic features * Inadequate response to current, ongoing antidepressant treatment as defined by protocol * Having at least one but no more than 2 antidepressant treatment trial failures * Body mass index (BMI) 18.0-35.0 kg/m2 inclusive Exclusion Criteria: * Patient currently receives treatment with a combination of 3 or more antidepressants * Significant ongoing use of high doses of barbiturates, benzodiazepines or other anxiolytic drugs * Patient previously received RO4995819 * Patient participated in an investigational drug or device trial within 6 months of screening * History of non-response to, or current use of non-pharmacological treatment including Electroconvulsive Therapy (ECT), Vagus Nerve Stimulation (VNS), or Repetitive Transcranial Magnetic Stimulation (RTMS) * Past or present psychotic symptoms