The purpose of the study is to evaluate the efficacy of study drug (BMS-820836) as compared with continued duloxetine in the treatment of patients with treatment resistant depression (TRD).

Inclusion Criteria:

• Patients must be able to understand the nature of the study, agree to comply with the prescribed dosage regimens, report for regularly scheduled office visits, and communicate to study personnel about adverse events and concomitant medication use.
• Patients with a diagnosis of Major Depressive Disorder, currently experiencing a Major Depressive Episode, as defined by Diagnostic and Statistical Manual of Mental Disorders- Fourth Edition Text Revision(DSM IV TR) criteria. The current depressive episode must be > 8 weeks in duration and < 3 years duration.
• In the current Major Depressive Disorder (MDD) episode, patients should report a history of inadequate response to 1 - 3 adequate trials of antidepressant treatment.
• Patients must have a 17-item Hamilton Depression Rating Scale (HAM-D17) total score =>18 at Screening.

Exclusion Criteria:

• Patients who report an inadequate response (less than 50% reduction in depressive symptom severity) to more than three adequate trials of antidepressant treatments during the current depressive episode.
• Patients who have failed duloxetine at an adequate dose and for an adequate duration in their current episode unless in the judgment of the investigator, the patient could benefit from the treatment with this medication.
• Patients whose only inadequate response to an antidepressant in the current Major Depressive Episode (MDE) is to an Serotonin norepinephrine reuptake inhibitors (SNRI) (duloxetine, venlafaxine, desvenlafaxine or milnacipran).