The Treatment of Depression With Yoga and Walking

Inclusion Criteria: * Subject is fluent in English. * Subject understands the risks and benefits of the study as listed in the Post Consent Quiz. * Females agree to use an acceptable form of birth control. * Female had a negative pregnancy test or serum progesterone \<= 0.30 ng/ml consistent with the non-luteal phase of the cycle prior to Scan 1. * Subject meets criteria for Diagnosis of Major Depressive Disorder on the SCID. * Subject had BDI-II score of at least 14 during screening. * Subjects who are prescribed a stable dose of antidepressants at least three months with no anticipated changes in their medications for the course of the study (i.e. 3 months after enrollment). * Subject who have been in a stable form of psychotherapy for three months with no anticipated changes in their psychotherapy for the course of the study (i.e. 3 months after enrollment). * Subject had given contact information. * Subject weighs up to 300 lbs at the discretion of the PI. * Subject has completed all required screening instruments and evaluations. Exclusion Criteria: * Subject has a history of psychosis. * Subject has a history of bipolar illness. * Subject has a history of suicidal ideation with intent in the last year according to the Columbia Suicide Safety Rating (C-SSR) scale. * Subject has a history of suicide attempt with attempt to injure in the last year according to the C-SSR. * Subject who wishes to be treated for MDD with a new treatment during the study such as pharmacotherapy, or somatic therapy or psychotherapy. * Subject has a contraindication to magnetic resonance evaluation (e.g. pregnancy, a cardiac pacemaker, ferrous implant including shrapnel, or intrauterine devices (IUDs) with copper, claustrophobia that would prevent scanning, some tattoos with black ink on the head including permanent eyeliner). * Subject has a current mind-body practice (e.g., Tai Chi, Qigong, breathing practices, meditation) defined as more than 6 one-hour sessions in the last 6 months. * Subject has a current prayer practice \> 2 hours a week (prayer group does not count, only prayer practice). * Subject participates in physical exercise \>5 hours/week that is equivalent to or greater than 6 metabolic equivalents (METs) in intensity. * Subject has been treated with mood stabilizers in the last three months (e.g., Topiramate, Valproic Acid, or Lithium). * Subject has been treated with medications known to influence the GABA system in the last three months (e.g., anti-anxiety agents such as benzodiazepines, some sleeping aids such as Ambien, or sedative hypnotics). * Subject uses nicotine regularly in the last three months. * Subject has a neurologic condition that would in the opinion of the PI would affect the results of the magnetic resonance spectroscopy (MRS) scans. * Subject has a medical condition that could compromise subject safety or the integrity of the study. * Subject has a history of having more than 5 alcoholic drinks on 3 or more occasions in the prior three months. * Subject in the opinion of the PI would not be expected to complete the study including scheduling related issues, whose safety would be jeopardized by participation or who would jeopardize the study protocol. * Subject has an Axis-I diagnosis, other than depression that in the opinion of the PI would interfere with the subject's participation in this study.