Application and efficacy of tDCS in pediatric patients with Autism Spectrum Disorder: a systematic review

Abstract

Objective: Autism Spectrum Disorder (ASD) is a neurodevelopmental condition characterized by persistent difficulties in social communication and interaction, along with restricted and repetitive patterns of behaviour. In recent years, transcranial direct current stimulation (tDCS) has emerged as a non-invasive neuromodulation technique with potential therapeutic applications in pediatric populations. The aim of this systematic review was to analyze recent scientific evidence regarding the application, efficacy, and safety of tDCS in children and adolescents diagnosed with ASD, to evaluate its potential as a complementary intervention to early therapeutic approaches. Participants & Methods: A systematic literature review was conducted following PRISMA guidelines. Searches were performed in PubMed, Scopus, and Web of Science. Additionally, a snowball search strategy was employed by manually screening the reference lists of the included studies to identify further relevant publications. Studies published between 2021 and 2025 in English were considered. Inclusion criteria comprised experimental or quasi-experimental studies evaluating tDCS in children and adolescents (1–18 years) diagnosed with ASD, reporting quantitative data on efficacy and/or safety. Narrative reviews, theoretical articles, studies conducted exclusively in adults or animals, and studies using neuromodulation techniques other than tDCS were excluded. After removing duplicates and screening titles, abstracts, and full texts, 15 studies met the eligibility criteria and were included in the final synthesis. Data were extracted regarding study design, sample characteristics, stimulation parameters, outcome measures, main findings, and adverse effects. Results: The included studies comprised randomized controlled trials, pilot studies, and quasi-experimental designs conducted across various countries, with sample sizes ranging from fewer than 20 to over 50 participants. Most studies applied anodal stimulation over the left dorsolateral prefrontal cortex, typically using 1 mA intensity for approximately 20 minutes across 10 to 20 sessions. Outcome measures primarily assessed core ASD symptoms, social behavior, executive functions, and attention, using standardized clinical scales and, in some cases, neurophysiological measures such as electroencephalography. Overall, findings suggest modest but relatively consistent improvements in social cognition, adaptive behavior, attention, and executive functioning in active stimulation groups compared to sham conditions. Neurophysiological changes associated with improved functional connectivity were also reported in some studies. Across all studies, tDCS demonstrated a favorable safety profile, with only mild and transient adverse effects such as tingling, itching, or mild scalp redness. However, methodological heterogeneity and small sample sizes limit the generalizability of findings. Conclusion: Current evidence suggests that tDCS may represent a promising and safe complementary intervention for children and adolescents with ASD, particularly when combined with established therapeutic approaches. Nevertheless, variability in stimulation protocols, outcome measures, and methodological quality highlights the need for larger, well-controlled trials to clarify its clinical efficacy and optimize treatment parameters.