Effects and neural correlates of tDCS on anhedonia in MDD: A randomized clinical trial

Transcranial direct current stimulation (tDCS) targeting the left dorsolateral prefrontal cortex (DLPFC) has been explored as a potential add-on therapy for anhedonia in major depressive disorder (MDD), a condition often resistant to conventional antidepressants. This study aimed to further evaluate the effects and neural correlates of adjunctive tDCS on anhedonia in MDD. This randomized, double-blind, sham-controlled study recruited 70 MDD patients, of whom 56 completed the protocol. Assessments were conducted at baseline and after two weeks of intervention, utilizing clinical evaluations for depression and anhedonia, alongside task- and resting-state EEG measurements. Our results demonstrated that adjunctive tDCS significantly improved overall depressive symptoms and anhedonia. Notably, we observed a more pronounced negative-going shift in Feedback-Related Negativity amplitude during the Guessing-Door Task and enhanced occipital alpha power spectral density in resting-state EEG. Moreover, increases in alpha activity were inversely correlated with subjective anhedonia severity, as measured by the Snaith-Hamilton Pleasure Scale. These findings suggest that adjunctive tDCS applied to the left DLPFC can effectively reduce symptoms of anhedonia in MDD patients, potentially through specific alterations in brain activity.