This study focuses on people with **Major Depressive Disorder (MDD)** who feel no pleasure (anhedonia) and aren't getting better with their current medicine, which includes types of antidepressants called **Selective Serotonin Reuptake Inhibitors (SSRI)** or **Serotonin Norepinephrine Reuptake Inhibitors (SNRI)**. **Major Depressive Disorder (MDD)** is a condition where someone feels very sad and loses interest in things they used to enjoy. **Anhedonia** means not feeling joy or excitement in things that once brought happiness. Participants need to start or plan to start a new treatment added to their current medicine to see if it helps better. 1. **Study Details**: Participants will follow their regular care while researchers collect information about their treatment responses. 2. **Eligibility**: Must have MDD without psychotic features and be on SSRI/SNRI for at least 6 weeks but not improving. 3. **Exclusions**: Those with certain mental health disorders, unstable medical conditions, or suicidal thoughts might not be eligible. Participants should discuss with their doctors to see if joining this study is a good choice for them.