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Graph theory reveals electroconvulsive therapy-induced whole-brain network integration and subnetwork changes in major depression and suicidality

Poster Session D - Monday, March 31, 2025, 8:00 – 10:00 am EDT, Back Bay Ballroom/Republic Ballroom

K. Tristan Donaldson¹ (ktdonaldson@mgh.harvard.edu), Shane W. Walsh¹, Anirudh Chinthakindi¹, Olivia J. Newman¹, Samadrita R. Chowdhury¹, Kristen K. Ellard¹, Joan A. Camprodon¹; ¹Massachusetts General Hospital and Harvard Medical School

Electroconvulsive therapy (ECT) effectively treats major depressive disorder (MDD), but its therapeutic mechanisms are unclear. Resting-state functional magnetic resonance imaging (rs-fMRI) and graph theory studies suggest ECT enhances whole-brain functional connectivity (FC) and reorganizes brain networks via generalized therapeutic mechanisms. While these effects may alleviate MDD symptoms, ECT’s impact on suicidality—a core MDD dimension—and disruptions in specific subnetworks like the reward circuit remain unexplored. We analyzed a harmonized cohort of 32 subjects (16 males, 16 females; mean age 33 years, SD 12) who underwent pre- and post-ECT scanning on a Siemens Magnetom 3.0T XR MRI system. Subjects were classified into High Suicidality Depressed (HSD) and Low Suicidality Depressed (LSD) groups using suicide-specific responses from the CHRT-SR (14) scale. Resting-state functional connectivity was computed for the whole-brain and a predefined reward network using Pearson correlations. Graph theory metrics—mean degree, clustering coefficient, and global efficiency—were applied to identify potential network-level biomarkers distinguishing suicidal types within MDD. Preliminary findings indicate that whole-brain functional connectivity analysis showed no significant pre- and post-ECT differences. However, graph theory revealed significant increases in mean degree and global efficiency, suggesting enhanced brain network integration and improved inter-regional communication. A decrease in clustering coefficient indicated reduced local connectivity and greater global integration. Preliminary reward network analysis suggests targeted effects on circuits involved in motivation and anhedonia. These results highlight ECT’s therapeutic mechanisms at global and circuit-specific levels, offering insights into MDD pathophysiology and suicide-specific risk.

Topic Area: METHODS: Neuroimaging