 - At the start of the ScreeningProspective observational Phase, participants must have had nonresponse less than or equal to 25 improvement to 1 but less than or equal to 8 oral antidepressant treatments taken at adequate dosage and for adequate duration, as assessed using the Massachusetts General Hospital - Antidepressant Treatment Response Questionnaire MGH-ATRQ and documented records by medical and pharmacyprescription records, or a letter from the treating physician, for the current episode of depression 