Study Comparing Magnetic Seizure Therapy (MST) to Electroconvulsive Therapy (ECT) for Depression in Older Adults

To evaluate the feasibility, tolerability and efficacy of Magnetic Seizure Therapy (MST) in elderly patients with a major depressive episode, who are randomly assigned to receive an acute course of MST or ECT. The investigators hypothesize: 1. MST and ECT will have similar antidepressant efficacy 2. MST will have less post-treatment amnesia than ECT as reflected in a primary measures of anterograde and retrograde amnesia following the acute treatment phase. 3. At follow up, MST will show a lesser degree of persisting deficit in measures of retrograde amnesia than ECT.

The purpose of this study is to compare the clinical efficacy and side effects of Magnetic Seizure Therapy (MST) and Electroconvulsive Therapy (ECT) in older adults currently experiencing a major depressive episode in the context of either unipolar or bipolar depression. ECT is known to be highly effective in treating depression, but it can have some adverse cognitive side effects. MST is a new form of convulsive therapy that is being developed as a means of improving the side effect profile of ECT so that more patients may benefit without suffering significant detrimental effects on cognition. Both ECT and MST rely on a therapeutic seizure, but they do so in different ways. In ECT, an electrical stimulator is used to pass electrical current between two electrodes placed on the surface of person's head, which causes some electricity to go through the brain and cause a seizure. In MST, a magnetic stimulator is used to create a magnetic field in a targeted area of the brain, which induces a small electrical field in the neurons that causes a seizure. Treatments will be administered three times a week. In addition to the treatment sessions, this study will involve a number of assessments at different time-points (i.e., baseline prior to treatment, post-treatment, 2 months post-treatment and 6 months post-treatment) that are used to evaluate the person's antidepressant response and the physical and cognitive side effects of treatment.