NMDA Modulation in Antidepressant Nonresponders With Major Depressive Disorder

This study tests whether a drug that works on the NMDA receptor in the brain (which regulates mood) can help people with major depression who have not responded to standard antidepressants. **You may be eligible if...** - You have been diagnosed with major depressive disorder (MDD) - At least one antidepressant has not worked for you at an adequate dose and duration - Your current medications have been unchanged for at least 8 weeks - Your depression symptoms score at a moderate-to-severe level on a clinical scale **You may NOT be eligible if...** - You have other psychiatric conditions that may confound the study - You recently changed antidepressant medications (within 8 weeks) Talk to your doctor to see if this trial is right for you.