Sorting the mind: cognitive enhancement through transcutaneous auricular vagus nerve stimulation: a systematic review and meta-analysis

Clinical Snapshot

Key Findings

• P Value: Not explicitly stated for primary outcome; Bayesian posterior probability P[μ>0] ≥ 0.93 across models; moderator analysis: healthy vs. clinical β=-0.001, p=.994

• Effect Size: Hedges' g = 0.41 (small-to-moderate effect); domain-specific: executive functions g=0.46, cognitive flexibility/learning g=0.53, working memory/attention g=0.19, social cognition/emotion regulation g=0.80

• Primary Outcome: Overall cognitive performance improvement with taVNS versus sham/control

• Nnt Or Sensitivity: NNT not calculable from reported data; Bayesian posterior probability P[μ>0] ≥ 0.93 provides probabilistic support for a positive direction of effect; high-intensity protocols (>1.0 mA) associated with larger effects (specific effect size not reported in abstract)

• Confidence Interval: Overall: 95% CI 0.30–0.53; executive functions: 0.27–0.65; cognitive flexibility: 0.32–0.75; working memory: 0.04–0.33; social cognition: 0.07–1.52

Clinical Application

taVNS is non-invasive, relatively low-cost, and does not require surgical implantation, making it theoretically feasible in outpatient and research settings. However, optimal dosing parameters (intensity, duration, electrode site) remain undefined, and no standardised clinical protocol exists. High-intensity protocols (>1.0 mA) appear more effective but tolerability data are not reported. taVNS devices are not currently listed on the Australian Register of Therapeutic Goods (ARTG) for cognitive enhancement indications, and no PBS-subsidised pathway exists. The TGA would require device-specific clinical evidence meeting conformity assessment standards before any therapeutic claim could be made. RACGP guidelines do not currently address taVNS for cognitive enhancement. Australian clinicians should regard this as an experimental intervention appropriate only within approved research protocols (HREC oversight). The evidence base does not yet support off-label clinical use. Researchers in Australia may consider engagement with the NHMRC for funding of adequately powered, diagnosis-specific RCTs. Adults with cognitive impairment or healthy individuals seeking cognitive enhancement; clinical samples (k=7) showed comparable effects (g=0.55, 95% CI: 0.31–0.79) to healthy cohorts, suggesting potential applicability across neuropsychiatric and neurodegenerative conditions, though diagnosis-specific evidence remains limited

Abstract

Transcutaneous auricular vagus nerve stimulation (taVNS) is a noninvasive technique engaging vagal afferents that may enhance cognition, but results vary across domains and samples. Following PRISMA, seven databases (inception-October 2025) plus registries and gray literature were searched. Random-effects meta-analyses (REML; Hedges' g) were complemented by Bayesian hierarchical models and sensitivity analyses. Fifty-three studies were included; 30 contributed quantitative data (>1,500 participants). taVNS was associated with improved cognitive performance overall (g = 0.41, 95% CI: 0.30-0.53; I2 = 51.4%). Effects were moderate for executive functions (g = 0.46, 95% CI: 0.27-0.65; I2 = 9.5%) and cognitive flexibility/learning (g = 0.53, 95% CI: 0.32-0.75; I2 = 52.9%), and small for working memory/attention (g = 0.19, 95% CI: 0.04-0.33; I2 = 14.9%). Social cognition/emotion regulation showed larger but imprecise effects (k = 3; g = 0.80, 95% CI: 0.07-1.52; I2 = 82.1%). Clinical samples benefited similarly (k = 7; g = 0.55, 95% CI: 0.31-0.79; I2 = 29.5%), with no difference from healthy cohorts (β = -0.001, p = .994). High-intensity protocols (>1.0 mA) yielded larger effects; mode, duration, and site were not moderators. Bayesian models supported effects (P [μ > 0] ≥ 0.93). taVNS is associated with statistically significant improvements in cognitive performance, strongest for executive control and adaptive learning. We propose a Vagal Neurocognitive Integration Model linking LC-NE arousal modulation to prefrontal control. Future diagnosis-specific, adequately powered trials with multimodal neuroimaging should refine mechanisms and dose-response.

References

1. 1.Liu, F., & Li, Y. (2026). Sorting the mind: cognitive enhancement through transcutaneous auricular vagus nerve stimulation: a systematic review and meta-analysis. Psychological Medicine. https://doi.org/10.1017/S0033291726105017