A Study of Aticaprant 10 Milligrams (mg) as Adjunctive Therapy in Adult Participants With MDD With Moderate-to-severe Anhedonia and Inadequate Response to Current Antidepressant Therapy

Inclusion Criteria: * Be medically stable on the basis of physical examination, medical history, vital signs, and 12-lead electrocardiogram (ECG) performed at screening and baseline * Have a Hamilton depression rating Scale 17 item (HDRS-17) total score of 20 or higher at the first and second screening interviews and must not demonstrate a clinically significant improvement (that is, an improvement of more than 20 percent \[%\] on their HDRS-17 total score) between the first and the second independent HDRS-17 assessments * Meet Diagnostic and Statistical Manual of Mental Disorders-5th edition (DSM-5) diagnostic criteria for recurrent or single episode major depressive disorder (MDD), without psychotic features, based upon clinical assessment and confirmed by the structural interview for DSM-5 Axis I disorders-clinical trials version (SCID-CT). Participants 65 years of age or older must have had the first onset of depression prior to 55 years of age * Is currently receiving and tolerating well any one of the following selective serotonin reuptake inhibitor (SSRI) or serotonin-norepinephrine reuptake inhibitor (SNRI) for depressive symptoms at screening, in any approved formulation and available in the participating country/territory: citalopram, duloxetine, escitalopram, fluvoxamine, fluoxetine, milnacipran, levomilnacipran, paroxetine, sertraline, venlafaxine, desvenlafaxine at a stable dose (at or above the minimum therapeutic dose per Massachusetts General Hospital Antidep…