Mode of action

This is unknown, but may relate to alterations in neurotransmitter sensitivity. ECT causes many physiological changes, including slowing of the EEG, and increased secretion of sympathetic amines, prolactin, and other pituitary hormones, but none of these correlate reliably with clinical response. Some sceptics claim that ECT is effective just because it results in confusion, which makes the patient forget depressing thoughts.

Production of an adequate fit, arbitrarily defined as a generalized tonic-clonic seizure lasting at least 25 seconds, appears to be necessary for a good clinical effect. The minimum size of electrical stimulus required to cause a fit varies a great deal between patients, and is influenced by many factors including age, medication, and previous exposure to ECT. Ideally, the stimulus should be individually adjusted to be slightly above the individual's seizure threshold. If the stimulus is too low, no fit occurs; if too high, marked confusion may follow the treatment.

Medications with anticonvulsant effects, such as benzodiazepines, should be stopped before treatment.

Research studies comparing real ECT with 'pseudo-ECT', in which an anaesthetic and muscle relaxant are given but no electric shock, shows that real ECT is more effective in the treatment of depression but 'pseudo-ECT' has some clinical benefit too (Butler et al., 2006). This suggests that factors such as the complexity and mystique of the treatment, the extra medical and nursing attention, and/or the anaesthetics are partly responsible for the therapeutic effect.

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