For induction of general anesthesia for ECT, patients will receive either 1mg/kg of methohexital (standard arm) or 1.0 mg/kg IV ketamine (experimental arm) intravenously (IV) for the duration of their ECT index course over 2-3 weeks. The primary outcome in this trial is change in symptoms of depression assessed by standard questionnaires: Patient Health Questionnaire 9 (PHQ9) and Hamilton Depression Rating Scale (HDRS) score changes from baseline and final ECT administration. Secondary outcomes are changes in cognitive status as assessed by the Montreal Cognitive Assessment (MoCA) scale, quality of seizures, changes in regional cerebral oximetry during and after seizure, changes in serum metabolites (including kynurenine, D/L-serine and other glutamate intermediates) after treatment, , and need for further ECT courses (relapse) within 1 year after initial course.