Neural Circuit Effects of Ketamine in Depression

This study is researching how ketamine — a medication being explored for treatment-resistant depression — affects brain circuits involved in mood. Researchers will use brain scans and other measurements to better understand why ketamine works for some people with depression, which could help develop better treatments in the future. Healthy volunteers are also being recruited for comparison. **You may be eligible if...** - You are 18 to 65 years old - You have been diagnosed with major depressive disorder (MDD) currently at moderate or greater severity (patient group) - OR you are a healthy volunteer without depression (comparison group) - You are able to give informed consent and follow study requirements - Women of childbearing age must use reliable contraception and have a negative pregnancy test **You may NOT be eligible if...** - You have a history of schizophrenia, bipolar disorder, psychosis, or a neurodevelopmental disorder - You have active suicidal thoughts or a recent history of suicide attempts - You have a history of ketamine, PCP, or other dissociative drug misuse - You have significant heart, liver, or kidney problems - You are currently pregnant or breastfeeding - You have a substance use disorder (other than mild alcohol or cannabis use) Talk to your doctor to see if this trial is right for you.