The unilateral and bilateral therapy differ in psycho-organic effects but have the same antidepressive efficiency. This is due to the facts that the organic effects are mainly caused by the electrical current whereas the antidepressive effect is dependent on the seizure activity. Compared to the bilateral treatment, unilateral gives reduced confusion, anterograde and retrograde amnesia as well as reduced experience of memory impairment. The difference is explained by a lower density of current in the brain. The unilateral treatment should be the treatment to be chosen. The antidepressive action of ECT fits the amine hypothesis, ECT causes a sustained increase of the synthesis of norepinephrine and of the sensitivity of amine receptors and creates conditions for alleviating both "low-output" and "low-sensitivity" depression. The antidepressive action is probably mediated by release of hypothalamic neurohormones.