Archival ReportHippocampal Volume Changes Following Electroconvulsive Therapy: A Systematic Review and Meta-analysis

BackgroundReduced hippocampal volume is one of the most consistent morphological findings in major depressive disorder. Electroconvulsive therapy (ECT) is the most effective therapy for major depressive disorder, yet its mechanism of action remains poorly understood. Animal models show that ECT induces several neuroplastic processes, which lead to hippocampal volume increases. We conducted a meta-analysis of ECT studies in humans to investigate its effects on hippocampal volume.MethodsPubMed was searched for studies examining hippocampal volume before and after ECT. A random-effects model was used for meta-analysis with standardized mean difference (SMD) of the change in hippocampal volume before and after ECT as the primary outcome. Nine studies involving 174 participants were included.ResultsTotal hippocampal volumes increased significantly following ECT compared with pretreatment values (SMD = 1.10, 95% confidence interval [CI] 0.80-1.39, z = 7.34, p < .001, k = 9). Both right (SMD = 1.01, 95% CI 0.72-1.30, z = 6.76, p < .001, k = 7) and left (SMD = 0.87, 95% CI 0.51-1.23, z = 4.69, p < .001, k = 7) hippocampal volumes were also similarly increased significantly following ECT. We demonstrated no correlation between improvement in depression symptoms with ECT and change in total hippocampal volume (β = −1.28, 95% CI −4.51 to 1.95, z = −0.78, p = .44).ConclusionsWe demonstrate fairly consistent increases in hippocampal volume bilaterally following ECT treatment. The relationship among these volumetric changes and clinical improvement and cognitive side effects of ECT should be explored by larger multisite studies with harmonized imaging methods.