This study is looking at people with Major Depressive Disorder (MDD) who don't feel better with their current medicine, like SSRIs or SNRIs. SSRIs (Selective Serotonin Reuptake Inhibitors) and SNRIs (Serotonin Norepinephrine Reuptake Inhibitors) are common medicines for depression. The study checks how people with MDD and anhedonia (loss of interest or pleasure) respond when their treatment is changed.

Key Points:

• The study is observational, meaning participants are only monitored; no new treatments are given by the study.
• Participants need to be ready to start a new add-on treatment while continuing their current medication.
• Participants must be able to understand and consent to take part in the study.

People with certain conditions or who have not responded to any antidepressant treatment before may not join. Participation involves monitoring your response to new treatment as per usual care by your doctor.