The Effectiveness of Transcranial Direct Current Stimulation (tDCS) in Enhancing Social Interactions in 6- to 10-Year-Old Boys with High-Functioning Autism Spectrum Disorder

Abstract

This study aimed to determine the effectiveness of transcranial direct current stimulation (tDCS) in improving overall social interaction and its components, including social reciprocity, social participation/avoidance, and negative or inappropriate social behaviors, in 6- to 10-year-old boys with high-functioning autism spectrum disorder. This quasi-experimental study employed a pretest-posttest design with a one-month follow-up and a waiting-list control group. The statistical population consisted of 6- to 10-year-old boys with high-functioning autism spectrum disorder attending specialized autism treatment and rehabilitation centers in Tehran between November 2025 and January 2026. Thirty eligible children were selected through purposive sampling and randomly assigned to an intervention group and a control group, with 15 participants in each. The intervention group received 10 tDCS sessions over four weeks, with a current intensity of 1 mA for 20 minutes per session. The anodal electrode was placed over the left dorsolateral prefrontal cortex at the F3 site. Social functioning was assessed using the Autism Social Skills Profile at pretest, posttest, and one-month follow-up. Data were analyzed using mixed repeated-measures analysis of variance and Bonferroni-adjusted pairwise comparisons in SPSS version 26. The group × time interaction was significant for the total social interaction score, F(2,56)=58.96, p<0.001, partial η²=0.678. Significant interaction effects were also found for social reciprocity, F(2,56)=39.47, p<0.001, partial η²=0.585; social participation/avoidance, F(2,56)=35.91, p<0.001, partial η²=0.562; and negative/inappropriate social behaviors, F(2,56)=27.88, p<0.001, partial η²=0.499. Bonferroni comparisons showed significant improvements from pretest to posttest and from pretest to follow-up in the intervention group for the total score and all three components (p<0.001), whereas posttest-to-follow-up differences were not significant. No significant changes were observed in the control group. Anodal tDCS over the left dorsolateral prefrontal cortex produced significant and relatively stable improvements in overall social interaction and its components in boys with high-functioning autism spectrum disorder, suggesting that tDCS may be considered a complementary intervention alongside educational and rehabilitation programs.