Electroconvulsive therapy increases cortical thickness in depression: A systematic review

Abstract Objective Electroconvulsive therapy (ECT) is one of the most studied and validated available treatments for severe or treatment-resistant depression. However, little is known about the neural mechanisms underlying the ECT treatment. This systematic review aims to critically review all structural magnetic resonance imaging studies investigating longitudinal cortical thickness (CT) changes after ECT in patients with unipolar or bipolar depression. Methods We performed a search on PubMed, Medline, and Embase to identify all available studies published before April 20, 2023. A total of 10 studies were included. Results The investigations showed widespread increases in CT after ECT in depressed patients, involving mainly the temporal, insular, and frontal regions. In five studies, CT increases in a non-overlapping set of brain areas correlated with the clinical efficacy of ECT. The small sample size, heterogeneity in terms of populations, medications, comorbidities, and ECT protocols, and the lack of a control group in some investigations limit the generalizability of the results. Conclusions Our findings support the idea that ECT can increase CT in patients with unipolar and bipolar depression. It remains unclear whether these changes are related to the clinical response. Future larger studies with longer follow-up are warranted to thoroughly address the potential role of CT as a biomarker of clinical response after ECT. Summations This review summarizes how ECT affects CT in patients with unipolar or bipolar depression. The areas that were predominantly affected by ECT were temporo-insular and frontal regions. An association between the antidepressant effect of ECT and CT changes was reported by half of the included studies. Identifying the possible cortical changes associated with the clinical efficacy of ECT opens new targets to ameliorate ECT protocols. Considerations The review is based on studies with small numbers of patients and considerable heterogeneity in terms of patients’ characteristics and ECT protocols. Most studies cited did not have a randomized design, thus reducing the strength of evidence supporting a causal link between ECT and CT changes.