Transcranial direct current stimulation in attention-deficit hyperactivity disorder: A meta-analysis of neuropsychological deficits

Mohammad Ali Salehinejad; Miles Wischnewski; Vahid Nejati; Carmelo M Vicario; Michael A Nitsche

doi:10.1371/journal.pone.0215095

Transcranial direct current stimulation in attention-deficit hyperactivity disorder: A meta-analysis of neuropsychological deficits

PLoS One. 2019 Apr 12;14(4):e0215095. doi: 10.1371/journal.pone.0215095. eCollection 2019.

Authors

Mohammad Ali Salehinejad^{1

2}, Miles Wischnewski³, Vahid Nejati^{4

5}, Carmelo M Vicario^{2

6}, Michael A Nitsche^{2

7}

Affiliations

¹ Ruhr-University Bochum, International Graduate School of Neuroscience, Bochum, Germany.
² Leibniz Research Centre for Working Environment and Human Factors, Department of Psychology and Neurosciences, Dortmund, Germany.
³ Donders Institute for Brain, Cognition, and Behaviour, Radboud University Nijmegen, The Netherlands.
⁴ Department of Psychology, Shahid Beheshti University, Tehran, Iran.
⁵ Department of Psychology, University of Regensburg, Regensburg, Germany.
⁶ University of Messina, Department of Scienze Cognitive della Formazione e degli Studi Culturali, Messina, Italy.
⁷ University Medical Hospital Bergmannsheil, Department of Neurology, Bochum, Germany.

Abstract

Transcranial direct current stimulation (tDCS) is a promising method for altering cortical excitability with clinical implications in neuropsychiatric diseases. Its application in neurodevelopmental disorders especially attention-deficit hyperactivity disorder (ADHD), is in early stage and promising but its effectiveness has not been systematically examined yet. We conducted a meta-analysis on the effectiveness of tDCS on the most studied neuropsychological symptoms of ADHD, which is the first reported meta-analysis of tDCS studies on ADHD. Data from 10 randomized controlled studies (including 11 separate experiments) targeting inhibitory control, and/or working memory (WM) in ADHD were included. Results show that overall tDCS significantly improved inhibitory control. Sub-analyses further show that dorsolateral prefrontal cortex (dlPFC) (but not right inferior frontal gyrus) tDCS and anodal (but not cathodal) tDCS significantly improved inhibitory control with a small effect size. Anodal dlPFC-tDCS had the largest significant effect on inhibitory control with a small-to-medium effect size. Additionally, a significant improving effect of tDCS on inhibitory control accuracy (but not response time) and WM speed (but not accuracy) were found. Overall, this meta-analysis supports a beneficial effect of tDCS on inhibitory control and WM in ADHD with a small-to-medium effect size. TDCS seems to be a promising method for improving neuropsychological and cognitive deficits in ADHD. However, there might be a dissociation between neuropsychological deficits and clinical symptoms of ADHD and therefore, the significance of this meta-analysis for clinical purposes is limited. Future studies should systematically evaluate the role of inter-individual factors (i.e., ADHD subtype, types of the deficit) and stimulation parameters (i.e., site, polarity, intensity, duration, repetition rate) on tDCS efficacy in ADHD population and examine whether benefits are long-term.

Publication types

Meta-Analysis
Research Support, Non-U.S. Gov't

MeSH terms

Attention Deficit Disorder with Hyperactivity / therapy*
Humans
Neuropsychological Tests
Prognosis
Transcranial Direct Current Stimulation / methods*

Grants and funding

Publication of this article was funded by the Open Access Fund of the Leibniz Association. MAS receives support from the National Organization of Science, Research & Technology, Deputy of Scholarship and Students Affairs, Iran, grant number: 95000171. The funder had no role in the study design, data collection, and analysis, decision to publish or preparation of the manuscript.