Transcranial direct current stimulation (tDCS) as an add-on treatment for restricted repetitive behaviors in autism spectrum disorder – An open-label prospective feasibility study

Introduction: Restricted and repetitive behaviors (RRBs) among autistic individuals can lead to significant distress and functional impairment and may include self-injurious behaviors. The study aimed to assess the feasibility, tolerability, and impact of transcranial direct current stimulation (tDCS) on RRBs and executive functioning. Methods: We conducted an open-label feasibility trial of add-on tDCS involving 10 sessions of anodal stimulation over the left dorsolateral prefrontal cortex and cathodal stimulation over the supplementary motor area in autistic adolescents with clinically significant and/or dysfunctional RRBs. RRBs were assessed using the Repetitive Behavior Scale-Revised (RBS-R), and executive functioning using the Behavior Rating Inventory of Executive Function-2nd edition (BRIEF-2)-parent report. Data were analysed using linear mixed-effect models. Results: The intervention was feasible, with 16 of 17 adolescents completing the protocol and follow-up assessments. No serious adverse effects were reported. At 1-week post-intervention, there was a significant reduction in RBS-R overall scores (β = −4.00, p < 0.001, ES = -1.60, 95% CI = -2.43, -0.78), with further improvement at 1-month (β = −7.13, p < .001, ES= -2.85, 95% CI = -3.81, -1.90), and sustained effects at 3-months (β = −7.00, p < .001, ES= -2.80, 95% CI = -3.77, -1.84). Executive functioning also showed significant improvement at 1- and 3-months. Conclusion: These preliminary findings suggest that add-on tDCS may improve RRBs and executive functioning in autistic adolescents. The large ES warrants cautious interpretation, given the open-label design, reliance on parent-rated measures, small sample size, and needs to be examined in randomised controlled designs. © 2026 Elsevier B.V.