ECT-induced EEG asymmetry and therapeutic response in melancholia: relation to treatment electrode placement.

Six right-unilateral and bilateral ECTs were equally effective in reducing Hamilton Rating Scale for Depression scores in 34 melancholic patients whose EEG symmetry did not change after ECT. However, a substantial therapeutic advantage was recorded for bilateral ECT in those patients whose EEG symmetry changed. Accentuation of ECT-induced EEG slowing over the right hemisphere was associated with right-unilateral ECT and a lesser treatment response, suggesting that the therapeutic advantage reported by some investigators for bilateral over right-unilateral ECT may be attributed to a poor outcome experienced by those unilateral ECT patients who developed right-sided EEG slowing.