Effects of Transcranial Random Noise Stimulation On Cognitive Functions in Healthy Adults: Evidence From A Systematic Review And Meta-analysis.

Transcranial random noise stimulation (tRNS) has attracted increasing attention as a neuromodulation tool; however, findings on its cognitive effects remain inconsistent. This study systematically reviewed and meta-analyzed the effects of tRNS on cognitive functions in healthy adults. A comprehensive search of the Cochrane Library, PubMed, EMBASE, and Web of Science databases was conducted up to September 15, 2025. Randomized controlled trials using either parallel or crossover designs were included. Data were analyzed using random-effects models. Thirteen randomized controlled trials involving 403 participants met the inclusion criteria. The pooled analysis showed a small positive but non-significant overall effect of tRNS on cognitive functions (Hedges' g = 0.17, 95% CI [-0.06, 0.40], p = 0.145). Subgroup analyses indicated that online stimulation produced a significant positive effect (Hedges' g = 0.37, 95% CI [0.04, 0.70], p = 0.026), whereas offline stimulation did not; however, the between-subgroup difference was not statistically significant. No significant differences were observed across cognitive domains, stimulation sites, or stimulation durations. Egger's regression test did not indicate significant publication bias. Overall, current evidence suggests that tRNS has limited and uncertain effects on cognitive functions in healthy adults. Larger, well-powered studies using standardized protocols and incorporating neurophysiological outcomes are needed.