A Standard of Care Study of Patients With Major Depressive Disorder Who Have Had an Inadequate Response to a Selective Serotonin Reuptake/Serotonin-Norepinephrine Reuptake Inhibitor Antidepressant

Open to people ages 18-74

• Has a diagnosis of Major Depressive Disorder (MDD) without psychotic features as confirmed by the Mini International Neuropsychiatric Interview (MINI)
• Treatment with an selective serotonin reuptake inhibitor (SSRI)/serotonin-norepinephrine reuptake inhibitor (SNRI) for at least 6 weeks at an adequate dose (per Massachusetts General Hospital-Antidepressant Treatment Response Questionnaire [MGH-ATRQ]). Specifically, one of the following in any formulation is allowed: SSRIs: citalopram, duloxetine, escitalopram, fluvoxamine, fluoxetine, milnacipran, levomilnacipran, paroxetine, sertraline; SNRIs: venlafaxine, desvenlafaxine, vilazodone, or vortioxetine
• In the opinion of the treating clinician, the participant requires augmentation of the current antidepressant treatment and plans to initiate augmentation treatment in the near future. The participant has agreed to receive augmentation treatment
• Is currently an outpatient receiving psychiatric care (not inpatient care settings)

• Has a body mass index (BMI) of 18-40 kilograms per meter square (Kg/m²), inclusive

• Taking more than one antidepressant (regardless of class) at therapeutic doses (therapeutic doses per MGH-ATRQ). A second antidepressant is allowed to be taken at a lower dose if for sleep or pain management
• Is currently taking a benzodiazepine at higher doses than the equivalent of 3 milligrams (mg) of lorazepam
• Current diagnosis of a psychotic disorder including MDD with psychosis, bipolar disorder, intellectual disability, dementia, autism spectrum disorder, borderline personality disorder, or somatoform disorders
• Has treatment resistant depression (TRD) as defined by lack of response (less than [<] 25 percent [%] improvement) of 2 or more antidepressants of adequate dose (per MGH-ATRQ) and duration (6 weeks) in this episode
• Current diagnosis of PTSD, obsessive compulsive disorder, fibromyalgia, anorexia nervosa, or bulimia nervosa. Participants may be enrolled if they have been in remission for the past year