Noninvasive Brain Stimulation in Attention-Deficit/Hyperactivity Disorder: A Systematic Review and Meta-Analysis of Treatment Efficacy and Targeting Strategies

OBJECTIVE: Noninvasive brain stimulation (NIBS) has emerged as a promising novel treatment for attention-deficit/hyperactivity disorder (ADHD). However, the precise effects of NIBS in ADHD as well as optimal stimulation protocols remain elusive. This systematic review and meta-analysis aimed to provide a rigorous evaluation and robust quantified evidence on the therapeutic efficacy of NIBS in ADHD. METHOD: A systematic search of PubMed, Web of Science, and Embase identified 59 studies (repetitive transcranial magnetic stimulation [rTMS]: 11; transcranial direct current stimulation [tDCS]: 35; other NIBS: 13). Of these, 33 randomized controlled trial studies (7 for rTMS, 26 for tDCS; 1,049 participants with ADHD) were included in meta-analyses of therapeutic efficacy. Subgroup analyses were performed to investigate the impact of stimulation targets on therapeutic outcomes, and meta-regression analyses were included to evaluate the dose-response relationship. RESULTS: NIBS has favorable tolerability, but evidence for its therapeutic efficacy in ADHD remains inconclusive. Meta-analyses indicated that rTMS was effective in alleviating inattention symptoms (Hedges' g = -1.44, p = .002), reducing hyperactivity/impulsivity symptoms (Hedges' g = -0.95, p = .005), and improving attention-related functions (Hedges' g = 0.53, p = .023), and tDCS showed therapeutic benefits in reducing hyperactivity/impulsivity symptoms (Hedges' g = -0.28, p = .024) and improving inhibitory control (Hedges' g = 0.39, p = .028). tDCS positioned over the left dorsolateral prefrontal cortex and right orbitofrontal cortex demonstrated significant effects in improving inhibitory control. No significant dose-response relationship was found for either tDCS or rTMS in ADHD. CONCLUSION: This meta-analysis supports the therapeutic potential of NIBS in ADHD, revealing domain-specific benefits across different stimulation devices and sites. Although more data are needed, NIBS shows promise as an intervention for ADHD. PLAIN LANGUAGE SUMMARY: This systematic review and meta-analysis investigated the role of noninvasive brain stimulation in the treatment of attention-deficit/hyperactivity disorder (ADHD). Drawing on data from 33 randomized controlled trial studies with 1,049 participants, the authors found that repetitive transcranial magnetic stimulation (rTMS) was associated with improved attention and reduced hyperactivity/impulsivity, while transcranial direct current stimulation (tDCS) helped enhance inhibitory control and reduce hyperactivity/impulsivity. The effectiveness was linked to which brain region was stimulated. These results suggest that noninvasive brain stimulation may be a valuable treatment option for individuals with ADHD, particularly for those who do not respond well to standard medications. STUDY REGISTRATION INFORMATION: Efficacy of Noninvasive Brain Stimulation and the Impact of Targeting in Attention Deficit/Hyperactivity Disorder: An Updated Systematic Review and Meta-Analysis; https://osf.io/bmhax DIVERSITY & INCLUSION STATEMENT: We worked to ensure sex and gender balance in the recruitment of human participants. We worked to ensure race, ethnic, and/or other types of diversity in the recruitment of human participants. We worked to ensure that the study questionnaires were prepared in an inclusive way. Diverse cell lines and/or genomic datasets were not available. We actively worked to promote inclusion of historically underrepresented racial and/or ethnic groups in science in our author group. We actively worked to promote sex and gender balance in our author group. While citing references scientifically relevant for this work, we also actively worked to promote inclusion of historically underrepresented racial and/or ethnic groups in science in our reference list. While citing references scientifically relevant for this work, we also actively worked to promote sex and gender balance in our reference list. The author list of this paper includes contributors from the location and/or community where the research was conducted who participated in the data collection, design, analysis, and/or interpretation of the work.