Home-based tDCS as an add-on to digital cognitive behavioral therapy application (dCBT app) in adults with ADHD: A sham-controlled randomized pilot study

Abstract Introduction: Over 30% of adults with Attention-Deficit/Hyperactivity Disorder (ADHD) show an insufficient response to standard pharmacological treatments, which underscores the need for evidence-based alternative interventions. Methods: In this sham-controlled study, 30 adult outpatients with ADHD were randomized to 12 weeks of active or sham transcranial direct current stimulation (tDCS) as add-on to a digital cognitive behavioral therapy application (dCBT app). Participants received either active (2 mA, 20 min/day, 5 days/week) or sham tDCS with anodal (left) and cathodal (right) stimulation applied over the dorsolateral prefrontal cortex (DLPFC). In parallel, access to the dCBT app was provided for three months. ADHD symptoms were measured before and after treatment and after a three-month follow-up using the Adult Self-Report Scale (ASRS v1.1). Results: All scales showed an improvement over time with medium-to-large within-subjects effects (Cohens d: -.48 to -.75), irrespective of group allocation. Two additional sensitivity analyses including (1) participants with over 75% of planned (sham)-tDCS sessions and (2) those who logged into the dCBT app on at least 5 days (median split) confirmed results. Response was observed in 1/15 (6.7%) of the tDCS group and 2/15 (13.3%) of the sham-tDCS group, with no difference between groups (p = .543, phi = -.111). Compliance to (sham-)tDCS was high. tDCS usability was rated marginally lower in the tDCS group. Conclusions: tDCS as an add-on therapy could not produce additional improvement in ADHS symptoms. The results are discussed in terms of contextual and patient-related aspects. ClinicalTrials.gov Identifier: NCT06766214.