 - Have had an inadequate response to at least 1 but no more than 2 antidepressants, administered at an adequate dose and duration in the current episode of depression, as assessed by the Massachusetts General Hospital-Antidepressant Treatment Response Questionnaire MGH-ATRQ. An inadequate response is defined as less than 50 percent reduction in depressive symptom severity, as assessed by the MGH-ATRQ. An adequate trial is defined as an antidepressant treatment for at least 4 weeks at at least the minimum therapeutic dose, as specified in the MGH-ATRQ, for any particular antidepressant. The inadequate response must include the participants current antidepressant treatment 