Physical activity, sedentary behavior, and cognitive function in children and adolescents: a scoping review of dose-response relationships, screen time interactions, and public health implications

Background: Physical inactivity among children and adolescents has reached critical levels worldwide, with approximately 81% of school-aged youth failing to meet the World Health Organization recommendation of at least 60 min of moderate-to-vigorous physical activity per day. At the same time, screen-based sedentary behaviors have increased substantially, raising concerns about their combined impact on brain development, cognitive processes, and behavioral regulation. Although extensive research exists, evidence regarding dose-response relationships, neurobiological mechanisms, and the moderating role of screen-related behaviors remains fragmented. Objectives: This scoping review aimed to systematically map the evidence linking physical activity and sedentary behavior with cognitive outcomes in children and adolescents, examine dose-response patterns, synthesize underlying neurobiological mechanisms (including brain-derived neurotrophic factor and neuroplasticity), and evaluate the moderating influence of screen time and smartphone-related behaviors. Methods: The review followed PRISMA-ScR guidelines and the Joanna Briggs Institute methodology. Six electronic databases (PubMed/MEDLINE, Scopus, Web of Science, SPORTDiscus, PsycINFO, and CINAHL) were searched for studies published between January 2000 and March 2026. Eligibility criteria were defined using the Population-Concept-Context framework. Two independent reviewers conducted screening, achieving strong inter-rater reliability (κ = 0.84). Results: Of 2,843 records identified, 60 studies met inclusion criteria across four thematic domains: physical activity and cognitive outcomes, dose-response parameters, neurobiological mechanisms, and screen-based sedentary behavior including nomophobia. Chronic physical activity, particularly in school-based and clinical ADHD settings, was consistently associated with executive function improvements across included systematic reviews and trials. Screen time exceeding 4 h per day was associated with anxiety, depressive symptoms, and attentional deficits in observational data. Evidence on exercise-induced BDNF upregulation, contingent on structured exposure (≥3 sessions/week, ≥12 weeks), is restricted to five pediatric RCTs and warrants cautious interpretation. Conclusion: This scoping review maps consistent associations between physical activity and improved cognitive function in youth, mediated through neurobiological pathways that vary in strength across study designs and populations. Excessive screen exposure is associated with cognitive risk in observational data. Integrated public health frameworks addressing physical activity, screen time, and sleep represent a priority direction for future longitudinal research and policy development.