Functional connectivity differences in patients with mood disorders: an exploratory fMRI study comparing electroconvulsive therapy with pharmacological treatment

Electroconvulsive therapy (ECT) has been shown to induce widespread dysregulation of network connectivity in patients with mood disorders. Nevertheless, the extent to which these functional changes contribute to patients' cognitive side-effects or depressive symptoms improvement remains unclear. This study investigated cross-sectional resting-state functional connectivity (rs-FC) differences in patients with mood disorders after their 8th ECT session (ECT group, n = 33) compared to those receiving pharmacological treatment (non-ECT group, n = 36) and healthy controls (n = 34). Furthermore, we explored the association of rs-FC differences with cognitive side-effects and depressive symptom improvements assessed longitudinally in the ECT group. We focused on analyzing rs-FC within- and between the default mode network (DMN), executive control network (ECN), and frontoparietal network (FPN). Additionally, we explored the association between significant rs-FC group differences and verbal memory decline, and depressive symptoms improvement from pre-to post-ECT within the ECT group. ECT-treated patients exhibited hyper-connectivity within the left-hemisphere FPN compared to those on pharmacological treatment, along with hypo-connectivity between ECN and FPN (p-corrected<0.02). Depressive symptoms positively correlated with rs-FC within the right-hemisphere FPN (p-corrected<0.04). Notably, rs-FC differences were unrelated to verbal memory decline or symptom improvement from pre-to post-ECT (p-corrected>0.1). Our findings highlight differences in brain connectivity between remitted patients after ECT and diagnosis-matched patients following standard pharmacological treatment. Further studies are warranted to investigate longitudinal rs-FC effects of ECT to identify biomarkers predictive of treatment response and the risk of cognitive side effects after ECT.