Intravenous Ketamine for Treatment-Resistant Depression

This study tests intravenous (IV) ketamine — a medication already used for anesthesia but now being explored as a fast-acting antidepressant — for people with treatment-resistant depression who have not responded to multiple standard antidepressants. **You may be eligible if...** - You have a diagnosis of major depressive disorder (without psychosis) - Your depression is severe (PHQ-9 score ≥ 15) - You have tried and failed at least two antidepressant treatments (medication, TMS, or ECT) in the current episode - You can understand English and pass a comprehension test about the study **You may NOT be eligible if...** - You have schizophrenia, bipolar disorder, active psychosis, or schizoaffective disorder - You have active PTSD symptoms - You have a BMI over 40 - You take high doses of benzodiazepines in the morning - You take certain medications that interact with ketamine (e.g., MAOIs, opioid blockers, certain seizure medications) within 2 weeks of treatment Talk to your doctor to see if this trial is right for you.