ECT is an effective psychiatric treatment for severe depression, mania, catatonic states, and, to a lesser degree, some schizophrenias. Complications are minimal and the risk of death extremely low, lower than that for an inadequately treated depression. However, some medical centers in the United States do not use ECT at all. The neurochemical mechanisms that underlie ECT remain unknown, but a cerebral seizure is essential. The average number of treatments is seven, spread over two to three weeks. All candidates for ECT should undergo a complete medical evaluation and give informed consent.