Memory performance in severely depressed patients treated by electroconvulsive therapy

Depression is accompanied by disturbed implicit (unconscious) and explicit (conscious) memory functions. The aim was the assessment of immediate and delayed verbal and visual memory functions, concentration/attention during the course of electroconvulsive therapy (ECT) treatment.

Twenty severely depressed, drug-treatment resistant, elderly patients were assessed with the Wechsler Memory Scale-Revised (WMS-R) before and at the end of the ECT series.

Patients revealed deficits in acquisition (immediate verbal and visual memory), attention/concentration, and retrieval of information (delayed memory) before ECT. After ECT, significant improvements were observed in immediate memory but not in delayed memory. Although higher total stimulation levels (millicoulombs) (P = 0.015) were associated with improvements in immediate visual memory, we found that longer duration of convulsions (P = 0.016) as well as lower levels of stimulation at last ECT (P = 0.036) were associated with improvements in immediate verbal memory. Moreover, we found that stimulation energy (millicoulombs) in total and at last ECT was the best predictor among several clinical and ECT parameters of improved visual memory and concentration and decreased verbal and general memory.

Prefrontal cortex-related memory processes, especially immediate memory encoding, improved after ECT, whereas long-term memory remained impaired, indicating that severely depressed patients remain cognitively inferior to normal subjects despite clinically successful treatment. This study may yield a better understanding of the time course of memory alterations in severely depressed patients receiving ECT. Improvement of immediate memory may be essential for establishing normal daily activities of life in the recovery phase of depression.