Sorting the mind: cognitive enhancement through transcutaneous auricular vagus nerve stimulation: a systematic review...

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.