Dissociable roles of frontal electroencephalography markers in depression: Predictive value of frontal alpha asymmetry and responsive changes in beta power following home-based brain stimulation.

BACKGROUND

Transcranial direct current stimulation (tDCS) is a promising intervention for major depressive disorder; however, electroencephalographic (EEG) predictors of treatment response remain incompletely understood. Therefore, this study aimed to identify EEG predictors of treatment response in this population.

METHODS

In this study, a subsample (n = 108) of individuals included in a multicenter, double-blind randomized controlled trial (N = 198) with baseline and week 6 EEG data was analyzed. Participants received either 6 weeks of active tDCS (6W-active; n = 65) or 3 weeks of active stimulation followed by sham stimulation (3W-active-sham; n = 43). Resting-state EEG features, including frontal alpha asymmetry (FAA) and relative alpha and beta power at F3/F4, were analyzed. Pearson correlation and hierarchical regression analyses were conducted to assess associations with week 6 depressive symptoms (measured using the Beck Depression Inventory-II [BDI-II]), while adjusting for baseline severity.

RESULTS

In the 6W-active group, greater left-lateralized FAA at baseline was significantly associated with lower BDI-II scores at endpoint. In contrast, no significant FAA-depression association was observed in the 3W-active-sham group; however, higher F3 relative alpha power was associated with greater symptom severity. Regression analyses identified FAA as a significant predictor of treatment outcome after controlling for baseline symptoms and other covariates.

CONCLUSIONS

Baseline FAA may serve as a clinically relevant EEG predictor of antidepressant response to tDCS. Moreover, EEG-symptom associations differed by stimulation duration, supporting the potential of EEG biomarkers to guide personalized neuromodulation strategies.

TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT05539131.