This two-center, between-subject, randomized, double-masked study (n=20) will provide the first evidence for the antidepressant efficacy of Magnetic Seizure Therapy (MST) and contrast the therapeutic properties and side effects of two forms of MST in patients in a major depressive episode (MDE).

Inclusion Criteria:

• Clinical diagnosis of major depressive episode, in the context of unipolar or bipolar disorder
• Age 18-75
• Use of effective method of birth control for women of child-bearing capacity
• Willing and capable of providing informed consent
• Convulsive therapy clinically indicated
• Hamilton Rating Scale for Depression (HRSD) ≥18 (24 item)

Exclusion Criteria:

• Current unstable or serious medical condition, or any comorbid medical condition that substantially increases the risks of ECT (such as acute myocardial infarction, space occupying brain lesion or other cause of increased intracranial pressure, unstable aneurysm or vascular malformation, poorly controlled diabetes mellitus, carcinoma, renal failure, hepatic failure)
• Pregnancy
• History of neurological disorder, epilepsy, stroke, brain surgery, metal in the head, or structural brain lesion
• Presence of devices that may be affected by rTMS (pacemaker, medication pump, cochlear implant, implanted brain stimulator)
• Breast-feeding
• History of head trauma with loss of consciousness for greater than 5 minutes
• History of schizophrenia, schizoaffective disorder, or rapid cycling bipolar disorder
• Vagus Nerve Stimulator implanted
• History of substance abuse or dependence in past 3 months
• Failure to respond to an adequate course of ECT in the current depressive episode
• History of ECT in the past 6 months