Researchers have captured the first direct images of how ketamine alters key brain receptors in people with treatment-resistant depression. The region-specific changes closely matched symptom improvements, offering new insight into how the fast-acting antidepressant works. Credit: Shutterstock Major depressive disorder (MDD) is a major global health problem and one of the leading causes of disability. About 30% of people diagnosed with depression develop treatment-resistant depression (TRD),