Ketamine in the Treatment of Depression

Depressed patients will be offered experimental treatment with a new, potentially fast-acting antidepressant called ketamine while being scanned by magnetic resonance imaging (MRI) to measure the chemical effect of the drug. Ketamine will be given in a dose of 0.0 (placebo), 0.1, 0.2, 0.3, 0.4, or 0.5 mg/kg. If a patient does not respond to ketamine after the first infusion, it may be because s/he received ketamine placebo or the dose of ketamine was too low. In that case, an optional second scan and infusion of active ketamine (0.5 mg/kg) will be offered. This second scan will occur no later than weeks after the first scan/infusion (as scheduling permits). There is no guarantee that the patient will respond to the second ketamine infusion. Patients enrolled in the study are eligible for up to 6 months treatment with their study psychiatrist after the ketamine infusion(s). Healthy Volunteers: Healthy controls will receive an infusion of ketamine at a single dose (0.5 mg/kg). Volunteers will only receive one MRI scan and infusion.