Studies of the cognitive effects of electroconvulsive therapy (ECT) have resulted in controversial findings up to now, partly because researchers and reviewers have not always made a clear distinction among various aspects of cognition and because there are many parameters involved in the administration of ECT that have a potential impact on cognition. The present study focused on the impact of sine and pulse waveforms on anterograde memory and nonmemory cognitive functions.
We assigned 18 patients with unipolar major depression or bipolar I or II disorder, most recent episode depressed, to receive sine wave or pulse wave ECT and assessed their cognitive function before and after ECT, using a neuropsychologic test battery that measured anterograde memory, attention, and executive functions. Outcomes were measured, on average, 8.2 days after the last ECT session.
Both waveforms were equally effective in alleviating depression. Those who received sine wave ECT showed statistically significant deterioration in attention and executive tasks, such as the Stroop test, which measures selective attention (P = 0.02), and the dual task, which taps divided attention (P = 0.01). On the other hand, those who received pulse wave ECT improved to a significant degree in certain memory tasks, such as visual memory (P = 0.01) and general memory (P = 0.01) of the Wechsler Memory Scale-Revised (WMS-R), as well as in the dual task (P = 0.01). The between-group comparison revealed robust superiority of the pulse wave over the sine wave in terms of the dual task (P = 0.004).
Anterograde memory improved to a statistically significant or nonsignificant degree at 1 week post-ECT in comparison with pre-ECT regardless of waveforms. Attention/executive functions tended to deteriorate with sine wave ECT but improved with pulse wave ECT.