Quantification of EEG changes following electroconvulsive therapy in depression

Frequency analysis of EEG was made during electroconvulsive therapy (ECT) in patients with depression. Acute effects were quantified by calculating differences of EEG power from before to after the induced seizure, and were found to correlate with the duration of the seizure but not with the time lapse following the seizure. Increases in delta power were much more pronounced at the end of the treatment series than at the beginning. Non-acute effects were quantified as the differences from before the first treatment to the pre-ECT EEG later in the series. Increases in delta power correlated with the accumulated seizure duration and positively with the time lapse from the previous seizure, suggesting that it takes considerable time for this effect to develop. The concept of two different sources of EEG slowing during the ECT series is supported by different correlations between acute and non-acute EEG slowing on the one hand and on the other symptoms of depression, anxiety, cognitive disturbances, and cerebral blood flow as presented elsewhere.