Effects and Mechanisms of Transcranial Direct Current Stimulation Combined with Dialectical Behavior Therapy Skills Training in Adults with Attention-Deficit/Hyperactivity Disorder

Abstract Adult attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder that frequently persists into adulthood and is associated with substantial impairments in academic, occupational, and social functioning. Although pharmacological treatment remains the primary intervention, some adults with ADHD show limited response to medication or experience adverse effects, highlighting the need for effective non-pharmacological or combined treatment approaches. Dialectical Behavior Therapy Skills Training (DBT-ST), which emphasizes emotion regulation, impulse control, mindfulness, and behavioral organization, has shown potential in the treatment of adult ADHD. However, its therapeutic efficacy may vary across individuals, and strategies to enhance treatment outcomes still require further investigation. In parallel, transcranial direct current stimulation (tDCS), a safe and non-invasive neuromodulation technique, has attracted increasing attention as an adjunctive intervention in psychiatric disorders. Existing studies suggest that combining tDCS with psychotherapy may optimize treatment effects by modulating neural networks related to cognitive control and emotional regulation. Nevertheless, evidence for such combined interventions in adult ADHD remains limited, particularly with respect to rigorous randomized controlled designs and mechanism-based neuroimaging validation.

The present study aims to investigate the efficacy and potential mechanisms of tDCS combined with DBT-ST in adults with ADHD. A randomized, double-blind, sham-controlled design will be adopted. Sixty eligible adult participants with ADHD will be randomly assigned to either an active tDCS group or a sham stimulation group, with both groups receiving weekly DBT-ST for ten consecutive weeks. tDCS will be administered over the bilateral dorsolateral prefrontal cortex (DLPFC) with 2 mA current for 20 minutes, prior to each group therapy session. Clinical symptoms, functional outcomes, and cognitive performance will be assessed at baseline, post-intervention, and one-month follow-up using standardized self-report measures and behavioral tasks. In addition, resting-state functional magnetic resonance imaging (rs-fMRI) will be conducted before and after the intervention to examine changes in functional connectivity within prefrontal regulatory networks.

This study is expected to clarify whether tDCS can enhance the therapeutic effects of DBT-ST on core ADHD symptoms and related functional outcomes, and whether such effects are associated with improvements in executive function, emotion regulation, and alterations in DLPFC-related resting-state functional connectivity. By integrating clinical, behavioral, and neuroimaging measures, the study seeks to provide preliminary evidence for a novel non-pharmacological combined intervention for adult ADHD and to further elucidate its underlying neural mechanisms.

Inclusion Criteria:

• Meet the diagnostic criteria for attention-deficit/hyperactivity disorder (ADHD) according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). Diagnosis confirmed using the Chinese version of the Diagnostic Interview for ADHD in Adults (DIVA-5).
• Aged between 18 and 55 years.
• Right-handed.
• Voluntary participation with provision of written informed consent.

Exclusion Criteria:

• Presence of neurological disorders or other psychiatric disorders.
• Severe physical illness.
• Receipt of electroconvulsive therapy (ECT) or other physical treatments within 6 months prior to enrollment.
• Planned changes in ADHD-related medication before the final follow-up assessment.
• Contraindications to tDCS (e.g., intracranial metal or electronic implants, skull plates, or other cranial implants).
• Pregnancy or breastfeeding.

Data sharing plans are currently undecided. Data may be made available upon reasonable request and subject to institutional approval and participant confidentiality considerations.