After providing informed consent, participants will complete brain MRI and memory testing. If they are currently taking an antidepressant and are not doing well on it, they will be taken off it. Participants will then start sertraline, a commercially available antidepressants. They will be monitored for response and side effects for 8 weeks and doses adjusted as needed. After the study, we will examine how differences in brain blood flow may predict who does and does not respond to sertraline.
