Mapping the Digital Mind: A Meta-Analysis of EEG Bi-omarkers in Cognition, Emotion, and Mental Health

Abstract Background: Electroencephalography (EEG) provides millisecond-resolution measure-ment of neural activity, offering unique potential for identifying biomarkers of cognition, emotion, and mental health. However, the proliferation of methodologically diverse stud-ies necessitates systematic synthesis to establish the reliability and clinical utility of pro-posed EEG biomarkers. Methods: Following PRISMA 2020 guidelines, we systematically searched PubMed, PsycINFO, Web of Science, and Scopus for studies published 2015-2025 examining EEG correlates of cognitive control, learning, emotion regulation, and mental health. From 3,847 initial records, k = 210 unique studies (N = 14,280 participants across 38 countries) met inclusion criteria. Random-effects meta-analyses estimated pooled effect sizes for primary EEG markers across five research domains. Results: Frontal-midline theta demonstrated robust effects for cognitive control (k = 12; d = 0.89, 95% CI [0.72, 1.07]; I2 = 0.0%) and learning/memory (k = 10; d = 0.70, 95% CI [0.50, 0.89]). The late positive po-tential indexed emotional processing (k = 18; d = 0.87, 95% CI [0.75, 1.00]) and regulation success (k = 14; d = -0.65, 95% CI [-0.79, -0.51]). Neurofeedback showed very large effects for PTSD (k = 2; d = -1.98, 95% CI [-2.50, -1.47]) and moderate effects for anxiety (d = -0.62), ADHD (d = -0.60), and depression (d = -0.42). Alpha event-related desynchronization marked cognitive engagement (k = 18; d = -0.70, 95% CI [-0.85, -0.55]). Heterogeneity was negligible (I2 = 0.0%) for most analyses, with clinical interventions showing condi-tion-explained heterogeneity (I2 = 75.4%). Conclusions: EEG biomarkers demonstrate sub-stantial effect sizes with remarkable consistency across cognitive and clinical domains, supporting their potential for diagnosis, treatment prediction, and intervention monitor-ing. A four-phase implementation framework is proposed to facilitate clinical translation. Future research should prioritize methodological standardization, diverse samples, and real-world validation. Keywords: electroencephalography; EEG biomarkers; cognitive control; frontal-midline theta; emotion regulation; late positive potential; neurofeedback; PTSD; mental health; systematic review; meta-analysis