Anodal transcranial direct‐current stimulation and non‐verbal intelligence in autism spectrum disorder: A randomized controlled trial

Abstract Aim To understand the impact of anodal transcranial direct‐current stimulation (tDCS) on non‐verbal intelligence in high‐functioning young adults with autism spectrum disorder (ASD). Method Thirty individuals with ASD were randomly divided into three groups receiving 2 mA, 20 minutes daily anodal tDCS for 10 sessions. Group A received 10 sham tDCS sessions, group B five real followed by five sham sessions, and group C received 10 real tDCS sessions. The total score of non‐verbal intelligence was measured using the Test of Nonverbal Intelligence, Fourth Edition. The left dorsolateral prefrontal cortex (LDLPFC) was targeted using the International 10–20 electroencephalography system, and concurrent cognitive training was avoided. Results Group C demonstrated a mean difference of 4.10 (95% confidence interval 1.41–6.79; p = 0.005) in Test of Nonverbal Intelligence scores compared with group A, with an effect size of 0.47. No significant differences were observed between groups A and B ( p = 0.296), or between groups B and C ( p = 0.140). Interpretation Ten sessions of anodal tDCS to the LDLPFC led to improved non‐verbal intelligence among individuals with ASD. These results emphasize the potential of tDCS as a discrete method for boosting cognitive abilities in the high‐functioning population with ASD. Future studies with larger groups of participants and extended observation periods are necessary to validate these findings.