Reduced Stimulus Dosage During ECT Lessens Memory Complaints

electro shock machine
electro shock machine

Reports of subjective memory problems were significantly reduced after new guidelines recommending a significantly lowered stimulus dose in electroconvulsive therapy were implemented, with no significant difference in effect on depressive symptoms, according to a study published in the Journal of Affective Disorders.

This retrospective register-based intervention study evaluated changes in the risk of worsening subjective memory after the electrical charges were lowered for participants during the administration of electroconvulsive therapy for depression. The primary study end point was worsening subjective memory; the secondary end point was the change in effect on depression.

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A total of 391 patients in the Swedish National Quality register for ECT received electroconvulsive therapy for a major depressive episode between April 2012 and April 2014 at Danderyds Hospital in Sweden. Participants were divided into a high dosage group who received treatment before the new guidelines and a low dosage group treated after the guidelines were implemented. Patients treated in both time periods were excluded. Memory changes were measured using scores before and after treatment that were based on the 7-point scale “failing-memory” item of the Comprehensive Psychopathological Rating Scale (CPRS-M), and effect on depression was measured using the Montgomery-Åsberg Depression Rating scale (MADRS-S).

Among a total 154 participants ultimately enrolled in the study, 57 were in the high dosage group and 97 were in the low dosage group. A significant difference in post-treatment CPRS-M scores was seen between the high and low dosage groups (Mdn=2, n=57; vs Mdn=1, n=97; U=1863.5, P <.001). When the incidence of worsening subjective memory was calculated (defined as a 2-point CPRS-M increase), a significant difference was seen between the 2 groups (χ2 [1, N=154]=6.05, P =.014), with 43.9% of high dosage participants experiencing memory worsening compared with 24.7% of low dosage participants (P =.014). There was no significant difference in antidepressant effect between groups.

Study limitations included the retrospective design, a potential sampling bias, and missing data. Despite these limitations, the investigators concluded that this study, “corroborates the correlation between a higher electrical charge and increased risk of negative effects on memory and contributes to the knowledge on optimal electrical stimulus dosage during ECT, for which there is not yet any clear consensus. Further studies are needed to investigate how short-term memory worsening after ECT relates to more persistent memory complaints.”


Kronsell A, Nordenskjöld A, Tiger M. Less memory complaints with reduced stimulus dose during electroconvulsive therapy for depression [published online August 20, 2019]. J Affect Disord. doi: 10.1016/j.jad.2019.08.064