Electroconvulsive therapy effects on anhedonia and reward circuitry anatomy: a dimensional structural neuroimaging approach

Anhedonia is a core symptom of major depressive disorder (MDD) resulting from maladaptive reward processing. Electroconvulsive therapy (ECT) appears to be an effective treatment for patients with treatment-resistant depression (TRD). However, no previous neuroimaging studies have taken a dimensional approach to assess whether ECT-induced gray matter (GM) volume changes are specifically related to improvements in anhedonia and positive valence emotional constructs. Here we aimed to assess the relationship between right unilateral (RUL) ECT-induced brain volumetric changes and improvement in anhedonia and reward processing in patients with TRD. We evaluated 15 patients at two time points (before the first ECT session and after acute ECT completion) using magnetic resonance imaging (MRI), clinical scales (i.e., Quick Inventory of Depressive Symptomatology [QIDS] for syndromal depression severity and Snaith-Hamilton Pleasure Scale [SHAPS] for anhedonia) and the Temporal Experience of Pleasure Scale (TEPS) for anticipatory and consummatory experiences of pleasure. Patients with TRD showed a significant improvement in anhedonia symptoms and both anticipatory and consummatory pleasure after RUL ECT completion. Moreover, GM volume increases within the right reward system were related to anhedonia responders and, specifically, improvement in anticipatory (but not consummatory) reward. We highlight the importance of a dimensional and circuit-based approach to understanding target engagement and the mechanism of action of ECT, with the goal to define symptom- and circuit-specific response biomarkers for device neuromodulation therapies.