The anticonvulsant hypothesis of the mechanisms of action of ECT: current status.

Electroconvulsive therapy exerts a variety of anticonvulsant effects. The linkage between specific anticonvulsant effects and the efficacy of ECT is examined in relation to changes in seizure threshold, seizure duration, and seizure expression, and alterations in cerebral blood flow (CBF) and metabolism, and in EEG slow-wave activity. New findings are presented that the magnitude of the change in seizure threshold over the ECT course is associated with therapeutic outcome, particularly with right unilateral (RUL) ECT. New findings also indicate that the change in seizure threshold covaries with the magnitude of global reductions in CBF over the treatment course, is inversely related to some inhibitory aspects of seizure expression, and is independent of the cumulative decrease in seizure duration. Considerable evidence has accrued associating the anticonvulsant and antidepressant effects of ECT. However, critical experiments should be conducted in which the effects of augmenting and blocking anticonvulsant actions are studied in relation to efficacy.