This article is from the Depression FAQ, by Cynthia Frazier with numerous contributions by others.
ECT is an effective form of treatment for people with depressions and other mood disorders. ECT may be used when a severely depressed patient has not responded to antidepressants, is unable to tolerate the side effects of antidepressants, or must improve rapidly. Some depressed people simply do not respond to antidepressants or mood controlling drugs, and ECT is a way for such people to be effectively treated. ECT is utilized in the treatment of both mania and depression. There are some people who because of severe physical illness are unable to tolerate the side-effects of the medications used to treat mood disorders. Many of these people can be successfully be treated with ECT. Pregnant women and people who have recently had heart attacks can be safely treated with ECT. Because of time pressure regarding occupational, social, or family events, some people do not have the time to wait for antidepressants or mood regulating medications to become effective. As ECT quite regularly brings about improvement within two or three weeks, people who are under such time pressure are also excellent candidates for ECT.