Near Infrared Spectroscopy (NIRS) for Assessment of Depression

This study is testing a non-invasive brain scanning technology called near-infrared spectroscopy (NIRS) — which uses light to measure blood flow in the brain — to see if it can better detect and assess major depression. Researchers will compare brain scans of people with depression to those without. **You may be eligible if...** - You are over 18 years old - You have a diagnosis of Major Depressive Disorder and are receiving treatment at the VA Medical Center (San Francisco), OR you are a healthy volunteer without depression **You may NOT be eligible if...** - You cannot sign informed consent - As a healthy volunteer: you have depression, anxiety, psychotic disorders, substance abuse, personality disorders, dementia, Alzheimer's disease, traumatic brain injury, stroke, or a brain tumor - As a depression patient: you have schizophrenia or another psychotic disorder, dementia or Alzheimer's disease, or other major brain disorders Talk to your doctor to see if this trial is right for you.