How Does ECT Work?

The major puzzle in ECT is its mechanism of action. How do seizures, which can be dangerous and damaging when they occur spontaneously, change a dysfunctional brain into one that performs normally? Why do repeated epileptic seizures relieve psychiatric disorders? The originator of the therapy, Ladislas Meduna, believed in a biological antagonism between mental illness and seizures, an antagonism we no longer consider credible. But though we may smile at this belief, we acknowledge that it led Meduna to devise methods to induce seizures safely, select patients who were likely to benefit, develop a plan for a successful course of treatments, demonstrate the safety of inducing seizures, evaluate the merits and risks of seizures as treatment, and convince others to continue his work. His observations have been repeatedly verified, leaving little doubt about the effectiveness of ECT in treating mental illnesses. We know a great deal about the essential features of a successful course of ECT. The generalized brain seizure is the central therapeutic event. The biochemical and physiological consequences of the seizure are the basis for the behavioral effects; neither anesthesia nor electric current alone is useful, nor, except rarely, is a single seizure. To be of benefit, seizures must be repeated two or three times a week for many weeks. The more recent the mood, thought, or movement disorder, the more fully it can be relieved. Illnesses involving lifelong problems, character pathology, neuroses, and the mood disorders secondary to the abuse of drugs are not amenable to this treatment. We know how to avoid the risks of anoxia, unmodified convulsions, and prolonged seizures, and we recognize that these aspects of the treatment course do not explain how ECT works. Two aspects of the brain seizure have been extensively studied. The EEG records electrical activity of the brain under electrodes that are symmetrically placed over the scalp. Immediately after the stimulus, the “seizure” EEG is recorded on a moving strip. The electrical waves show a sharp buildup of frequencies and amplitudes, then the frequencies slow, mixtures of slow brain waves and sharp spike-like waves appear, with ever higher amplitudes and slower waves in runs and bursts.