Day -4 to 0: Screening (visit 1) will occur three to six days prior to the first ECT treatment. Screening procedures will include: Psychiatric interviews and ratings (including MINI, Hamilton Depression Rating Scale and Clinician's Global Impression) and review/retrieval of results of pre-ECT physical exam, ECG, chest x-ray, laboratory evaluations (including comprehensive metabolic panel, comprehensive blood count, and urine toxicology), and vital signs from the subject's medical record. A urine pregnancy test will be included for females of childbearing potential. Concomitant medications and pre-existing health issues will be recorded. Subjects who are deemed eligible for this study will then undergo a battery of neuropsychiatric assessments and will be admitted to GCRC for collection of blood samples to measure adrenocorticotropin (ACTH) and cortisol levels. These samples will be collected hourly beginning at 1pm and ending at 4pm.