Transcranial Direct Current Stimulation of the Temporoparietal Junction in Autism Spectrum Disorder: Results of a Phase-IIa Randomized, Double-Blind, Sham-Controlled Feasibility Study

Activation of the temporoparietal junction (TPJ) is reduced in autism spectrum disorder (ASD) during social cognitive tasks. Therefore, anodal transcranial direct current stimulation (tDCS) of the TPJ may enhance social cognitive abilities in autistic individuals. In a multicenter, randomized, sham-controlled, double-blind parallel-group Phase-IIa trial, we investigated feasibility, safety, and effect sizes of 10 sessions of anodal tDCS of the bilateral TPJ at 2 mA as an add-on to computer-based social cognitive training in 10- to 17-year-old youth with autism. Feasibility of recruitment was low, with only 11% of screened individuals being randomized to tDCS (N = 12) or sham (N = 12). In contrast, retention in the study, data collection, intervention adherence, and technical feasibility were mostly excellent. No serious adverse events occurred, and stimulation was well tolerated. There were no differences in the prespecified primary outcome social responsiveness between sham and tDCS immediately after the intervention (standardized estimated effect size [ES] = 0.098; 95%-confidence interval [95% CI] −1.043;1.240), but the sham group showed a trend for better social responsiveness at the 4 week follow-up (ES = 1.106; 95% CI −0.054; 2.270). Secondary outcomes including questionnaires and event-related potentials showed improved compulsive behavior and quality of life by tDCS. High technical feasibility, participant retention, and safety highlight the potential of tDCS in autism and may inform future improvements in the feasibility of recruitment. The differential pattern of effect estimates indicates positive, but also potential negative effects of tDCS, which may vary due to tDCS stimulation parameters. The trial was prospectively registered in the German Clinical Trials Register (Deutsches Register für klinische Studien, DRKS, DRKS00014732).