Opinion is divided over the effectiveness of using electroconvulsive therapy (ECT) to treat severe depression that has not responded to other forms of therapy.

Use of the therapy is controversial mainly due to concerns about its efficacy and side effect profile. ECT alone does not usually provide a sustained benefit and those who remit often suffer a relapse of their condition within six months.

In 1999, a report from the United States Surgeon General on Mental Health summarized the opinion of psychiatrists regarding ECT at that time. This report stated that ECT was an effective treatment for severe depression, mania and some states of psychosis, leading to remission in 60% to 70% of cases.

The therapy was not shown to be effective, however, as a treatment for dysthymia, anxiety disorder, personality disorder or substance abuse. Furthermore, the report said that the therapy has no long-term effect in terms of preventing people form committing suicide and can only offer a short-term benefit for an acute episode of illness. Follow-up therapy would therefore be required in the form of medication of further monthly or weekly ECT.

A 2003 report from the United Kingdom came from the UK ECT Review group who compared literature on the efficacy of ECT versus placebo. This report demonstrated that ECT was significantly more effective than placebo or antidepressant medication.

Another major report followed in 2004. A multicenter follow-up study of New York patients who had undergone ECT showed that only 30% to 47% of individuals remitted. However, when individuals with personality disorders or schizoaffective disorder were omitted from the analysis, the remission rate increased by as much as 70%.