Transcranial direct current stimulation (tDCS) combined with cognitive training in adolescent boys with ADHD: a double-blind, randomised, sham-controlled trial

Abstract

ABSTRACTBackgroundTranscranial direct current stimulation (tDCS) could be a side-effect free alternative to psychostimulants in Attention-Deficit/Hyperactivity Disorder (ADHD). Although there is limited evidence for clinical and cognitive effects, most studies were small, single-session, and stimulated left dorsolateral prefrontal cortex (dlPFC). No sham-controlled study has stimulated right inferior frontal cortex (rIFC), which is the most consistently under-functioning region in ADHD, with multiple sessions of anodal tDCS combined with cognitive training (CT) to enhance effects.Objective/HypothesisTo investigate clinical and cognitive effects of multi-session anodal tDCS over rIFC combined with CT in a double-blind, randomised, sham-controlled trial (RCT).Methods50 boys with ADHD (10-18 years) received 15 weekday sessions of anodal or sham tDCS over rIFC combined with CT (20mins, 1mA). ANCOVA, adjusting for baseline measures, age, and medication status, tested group differences in clinical and ADHD-relevant executive functions at posttreatment and after 6-months.ResultsADHD-Rating Scale, Conners ADHD Index, and adverse effects were significantly lower at post-treatment after sham relative to real tDCS. No other effects were significant.ConclusionsThis rigorous multi-session RCT of tDCS over the rIFC in ADHD combined with CT, showed no evidence of improvement of ADHD symptoms or cognitive performance. Findings extend limited meta-analytic evidence of cognitive and clinical effects in ADHD after 1-5 tDCS sessions over mainly left dlPFC. Given that tDCS is commercially and clinically available, the findings are important as they suggest that rIFC stimulation may not be indicated as a neurotherapy for cognitive or clinical remediation for ADHDHighlightstDCS has been suggested as an alternative treatment for ADHDWe combined 15-session anodal tDCS over the rIFC with cognitive training in ADHD childrenReal versus sham tDCS showed no cognitive or symptom improvementsConversely, real tDCS showed lower ADHD symptoms and higher adverse effectsMulti-session tDCS of rIFC shows no clinical or cognitive benefits in ADHD