Multimodal magnetic resonance imaging outcomes of transcranial direct current stimulation in psychiatric and neurological disorders: a systematic review.

INTRODUCTION

Transcranial direct current stimulation (tDCS) is a promising neuromodulation technique for psychiatric and neurological disorders, but its clinical efficacy is heterogeneous. Magnetic resonance imaging (MRI) can be used to identify response predictors and understand underlying mechanisms.

METHODS

A systematic review was conducted (PubMed/Web of Science/Embase) from inception to May 2025. Nineteen randomized clinical trials (RCTs) were included, using MRI methods to investigate tDCS effects for major depressive disorder (MDD), schizophrenia, alcohol use disorder (AUD), stroke, epilepsy, and fibromyalgia.

RESULTS

Outcomes focused on pre and post effects (n = 9), baseline MRI-based predictors (n = 7), or both (n = 3). Quality assessment showed that most studies (68.4%) had a low risk of bias. Functional MRI was the most frequent modality, followed by structural MRI. Besides methodological differences, findings were heterogeneous. Although some brain markers were identified, such as baseline brain structure in MDD, functional connectivity changes in schizophrenia and AUD, and motor network modulation in stroke, the strength and direction of these effects varied across studies.

CONCLUSIONS

Significant heterogeneity and limited MRI-tDCS trials currently hinder mechanisms and biomarker establishment of tDCS. Future research should focus on standardizing MRI acquisition and analysis, which can improve reproducibility, and support robust findings.