Modulating Delay Discounting in ADHD: A Multi-Sessional tDCS Intervention

Background Individuals with Attention-Deficit/Hyperactivity Disorder (ADHD) often exhibit delay discounting, a preference for smaller immediate rewards over larger delayed rewards, which is linked to executive function deficits and impulsive decision-making. The right dorsolateral prefrontal cortex (rdlPFC) plays a crucial role in cognitive control and impulse regulation, making it a potential target for non-invasive brain stimulation interventions. Objective This study aimed to investigate the effects of anodal transcranial direct current stimulation (tDCS) over the rdlPFC on delay discounting in children with ADHD. We hypothesized that active tDCS would enhance cognitive control, reducing impulsivity and increasing the selection of delayed rewards. Methods Using a single-blind, randomized parallel-group design, twenty-one children with ADHD (aged 7–12 years) were randomly assigned to either the active tDCS or sham stimulation group. The intervention consisted of 10 sessions of 1 mA anodal tDCS applied to the rdlPFC over three weeks. Participants completed a Chocolate Delay Discounting Task (CDDT) at three time points: pre-intervention, post-intervention, and two-month follow-up. A mixed ANOVA was conducted to examine the effects of tDCS on delay discounting rates (K index) across conditions. Results The interaction between group and time was significant for the total K index (F = 4.3, p < 0.02, ηp² = 0.18) and the 20-chocolate K index (F = 3.2, p < 0.05, ηp² = 0.14), indicating that anodal tDCS increased the likelihood of selecting delayed rewards compared to the sham condition. However, the main effects of group and time were not significant. No significant differences were observed for the 10-, 5-, and 2-chocolate K indices. Conclusion These findings suggest that anodal tDCS over the rdlPFC reduce delay discounting in children with ADHD, particularly in high-reward scenarios. Given the long-term follow-up results, tDCS could serve as a promising intervention for addressing impulsivity-related deficits in ADHD.