While depression can be effectively treated in the majority of patients by medication and psychotherapy, up to 20% of patients fail to respond. Electroconvulsive Therapy (ECT) is effective in approximately 70% of cases where antidepressant medications do not provide sufficient relief of symptoms. However, as many as 20-50% of the people who respond well to a course of ECT relapse within 6 months, therefore, periodic maintenance therapy is often required.