Effects of transcranial direct current stimulation (tDCS) combined with cognitive therapy in individuals with cognitive impairment: a systematic review and meta-analysis.

BackgroundCognitive impairment poses a significant challenge to healthcare systems worldwide, impacting patient autonomy, social participation, and quality of life, while placing a considerable burden on caregivers. Non-pharmacological interventions, particularly cognitive training and non-invasive brain stimulation, have emerged as promising therapeutic strategies. ObjectiveThis study aims to quantify the synergistic effects of transcranial direct current stimulation (tDCS) with cognitive training on cognitive function across a spectrum of pathologies that induce cognitive impairment. MethodsWe conducted a systematic review and meta-analysis following PRISMA guidelines. We searched PubMed for randomized controlled trials that investigated the effect of combined tDCS and cognitive training compared with cognitive training alone. The analysis was based on the GRADE framework for systematic reviews and meta-analyses. ResultsAcross 27 studies including 1,012 participants, tDCS combined with cognitive training showed a small effect compared with cognitive training alone (SMD = 0.36, 95% CI: 0.15-0.56). The effect was found only immediately after the intervention and declined during follow-up. ConclusiontDCS combined with cognitive training may provide a small, short-term benefit for cognitive function, but high heterogeneity across studies and loss of effect at follow-up underscore the need for larger, better-standardized trials to clarify its clinical value. Highlights- Combined tDCS and cognitive training produce a small but statistically significant short-term improvement in global cognitive performance. - Effects attenuate over time, highlighting limited durability without sustained or maintenance interventions. - High methodological heterogeneity and very low certainty of evidence limit broad clinical generalization.