Comparative Analysis of Heart Rate Variability across Cognitive Domains in Individuals with Autism and ADHD: A Systematic Review and Meta-Analysis

Neurodevelopmental disorders, such as autism spectrum disorder (ASD) and attention-deficit/ hyperactivity disorder (ADHD), are associated with neurocognitive deficits across multiple domains. In this context, heart rate variability (HRV) has emerged as a promising biomarker for cognitive function, yet meta-analytic studies examining HRV changes during cognitive tasks in these populations remain limited. To address this gap, we conducted a pre-registered systematic review and meta-analysis examining HRV changes in ASD and ADHD populations during cognitive tasks compared to neurotypical individuals and their own resting states. A comprehensive database search was conducted in Medline, Embase, PsycInfo, CINAHL, Scopus, and Google Scholar. A total of 20 studies, comprising 2,223 participants, met the inclusion criteria. The overall effect of HRV differences during cognitive tasks was not statistically significant when compared to neurotypical individuals (Hedges' g = -0.38 \textit{p} = .08). However, subgroup analyses revealed variation in effects, with significant differences observed in the ASD population (Hedges' g = -0.32, \textit{p} $<$ .01). Robust Bayesian analysis provided weak to moderate support against publication bias (BF = 0.38). Despite limitations including heterogeneity across studies and methodological inconsistencies in HRV measurement, these findings highlight the potential relevance of HRV in understanding cognitive functioning in neurodevelopmental disorders. Future research should aim to refine methodological approaches, explore longitudinal changes, and better control of confounding variables to deepen our understanding of autonomic regulation in ASD and ADHD populations.