Enhanced attention-dependent auditory processing by electroconvulsive therapy in psychotic depression

There is a lack of knowledge about the effect of electroconvulsive therapy (ECT) on auditory event-related potentials (ERPs) in severe psychotic depression. The aim of this study was to investigate both the effect of ECT on attention-dependent ERP (P300) and the correlation of P300 values with depression level. We recorded the auditory ERPs of 23 patients expressing psychotic symptoms and fulfilling the DSM-III-R criteria for treatment-resistant severe major depressive episode before and a week after successful bitemporal ECT. The clinical status was assessed with Hamilton (Ham-D) and Montgomery and Asberg (MADRS) depression scales. ECT was clinically very effective with these scales. On the level of auditory processing, ECT increased P300 amplitude with no significant effect on latency. Small amplitudes over the left hemisphere before treatment were associated with bigger Ham-D-score decrement. ECT produces a significant increase in brain activity at the level of attention-dependent auditory processing in severe depression. The change in electrical responses seems to represent a largely independent variable from the clinical assessment scales, even if the recovery rate was remarkable, because the change in overall symptom scores did not correlate with the P300 changes.