REVIEW OF: Gryglewski G et al, Brain Stimul 2021;14(4):927–937

STUDY TYPE: Meta-analysis

Electroconvulsive therapy (ECT) has high antidepressant potency, boasting an impressive response rate of up to 80%. However, despite decades of research, we still have little understanding of its mechanism of action. Although several structural brain changes have been observed following ECT, it is unclear which of these processes underlie its antidepressant effects and which processes might be secondary, or even irrelevant.

A new meta-analysis of 21 studies (n = 543 patients with depression) sought to answer this question. In all of these studies, patients received magnetic resonance imaging (MRI) both before and after ECT. The researchers reported that various brain regions increased in size after ECT, including the left and right hippocampus, the amygdala, CA1, CA2/3, the dentate gyrus, and the subicula. The hippocampus plays an important role in emotional regulation and memory consolidation and is one of the major brain areas involved in stress-related conditions like depression.

The authors could find no specific correlation between any brain changes and symptom improvement. While it may seem reassuring that ECT is associated with volumetric increases in brain areas rather than shrinkage, we still don’t know what those increases mean and cannot conclude that ECT is neuroprotective.

CARLAT TAKE
Although it is good to know that ECT does not lead to shrinkage of brain volume, we are still stumbling in the dark when it comes to understanding how this intervention works.