BMC Psychiatry. 2026 Jul 22;26(1):559. doi: 10.1186/s12888-026-08409-y.
ABSTRACT
BACKGROUND: The gut microbiota is intricately implicated in the pathogenesis of Major Depressive Disorder (MDD), with the vagus nerve serving as a key regulatory bridge. Transcutaneous Auricular Vagus Nerve Stimulation (taVNS) has emerged as a promising non-invasive therapeutic strategy for MDD by modulating the gut-brain axis, yet the precise brain-gut interaction mechanisms underlying its antidepressant effects remain poorly characterized. This study is a registered clinical trial (ChiCTR2200059591; Registered 4 May 2022; https://www.chictr.org.cn ).
OBJECTIVE/HYPOTHESIS: This study aimed to verify the clinical efficacy of taVNS for MDD and elucidate the underlying brain-gut crosstalk mechanisms, by integrating comprehensive clinical assessments, resting-state functional magnetic resonance imaging (rs-fMRI) neuroimaging data and gut metagenomic profiling.
METHODS: Ninety-five patients diagnosed with MDD were randomly allocated at a 1:1 ratio to either the active taVNS group (auricular concha stimulation) or the sham taVNS group (superior concha of mid-helix stimulation). Eighty patients (40 per group) completed the entire intervention course and were included in the final statistical analysis. All participants underwent 30-minute stimulation twice daily (4/20 Hz, 3-8 mA) for 8 consecutive weeks (5 days per week). Standardized clinical assessments were administered at baseline and post-intervention, including the 17-item Hamilton Depression Rating Scale (HAMD-17), 14-item Hamilton Anxiety Rating Scale (HAMA-14), and Gastrointestinal Symptom Rating Scale (GSRS). Rs-fMRI was performed to quantify core neural activity metrics, including amplitude of low-frequency fluctuation (ALFF), fractional ALFF (fALFF), regional homogeneity (ReHo), and degree centrality (DC); fecal samples were collected for high-throughput metagenomic analysis. Spearman correlation analysis and mediation analysis were further conducted to dissect the interactive relationships between brain neural activity and gut microbiota.
RESULTS: The active taVNS group achieved significantly superior clinical efficacy relative to the sham group, with a HAMD-17 response rate of 62.50% and remission rate of 35.00%, versus 30.00% and 2.50% in the sham group (all P < 0.05). Rs-fMRI analyses revealed significant group×time interaction effects on neural activity: decreased ALFF in the right calcarine sulcus; altered fALFF in the right inferior temporal gyrus, left cuneus, right superior frontal gyrus (SFG) and right angular gyrus; reduced ReHo in the right calcarine sulcus and bilateral insula; and increased DC in the right caudate nucleus and left anterior cingulate gyrus. Gut microbiota profiling identified anaerobic butyrate-producing bacteria and Faecalibacterium prausnitzii as potential biomarkers linked to taVNS therapeutic effects. HAMD-17 scores were negatively correlated with Faecalibacterium prausnitzii abundance (r=-0.566, P < 0.01) and positively correlated with anaerobic butyrate-producing bacteria abundance (r = 0.406, P < 0.01). Mediation analysis suggested that fALFF values in the right SFG may indirectly modulate depressive symptoms via regulating Faecalibacterium prausnitzii abundance (indirect effect 95% CI: 0.3039-2.4466), with a significant partial mediation effect observed, though future studies controlling for dietary and other confounding variables are needed to confirm this relationship.
CONCLUSION: taVNS effectively alleviates depressive symptoms in MDD patients via dual complementary pathways: directly modulating neural activity in the right SFG to regulate depression-related brain function, and indirectly maintaining gut microbiota homeostasis by enriching beneficial taxa such as Faecalibacterium prausnitzii. These findings provide novel mechanistic insights into the brain-gut interaction underlying the antidepressant effects of taVNS, laying a theoretical foundation for its clinical application in MDD management.
PMID:42487113 | DOI:10.1186/s12888-026-08409-y
