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

Abstract

BackgroundTranscranial 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

Neuroimaging and neurotherapeutics for Attention Deficit Hyperactivity Disorder (ADHD)

“…There was also no superior effect of real versus sham tDCS on a large battery of executive functions. While side effects did not differ between groups, the real tDCS group had worse adverse events related to mood, sleep and appetite (43). To conclude, there is large heterogeneity in tDCS studies with respect to study designs, stimulation parameters and site of stimulation which makes comparability between studies difficult.…”

“…One study found an improvement with transcranial random noise stimulation (tRNS) of left DPFC and right IFC compared to tDCS of left DLPFC combined with cognitive training on ADHD symptoms in 19 patients (42). However, the largest study that tested 15 sessions of tDCS of right IFC in 50 ADHD patients found no improvement compared to sham in clinical symptoms and even an improvement with sham relative to tDCS (43).…”

Effects of Transcranial Direct Current Stimulation in Children and Young People with Psychiatric Disorders: A Systematic Review

“…Of the nine RCTs, overall risk-of-bias was rated as "high" in five studies [32,33,36,52,56]; two with "some concerns" [37,39], and two with "low" [29,38] (see Supplementary Material S2). The non-randomised, controlled clinical trial was rated with moderate risk of bias [54].…”

“…Two double-blind RCTs applied tDCS to the inferior frontal cortex (IFC). The largest RCT in CYP with ADHD (n = 50) administered 15 sessions of anodal or sham tDCS to the right-IFC with concurrent cognitive training [39]. Compared to sham, the tDCS group showed significantly higher parent-rated ADHD symptoms immediately after stimulation, but not at a 6-months follow-up.…”

“…Compared to sham, the tDCS group showed significantly higher parent-rated ADHD symptoms immediately after stimulation, but not at a 6-months follow-up. No significant differences were reported in other measures of ADHD symptoms or related impairments [39]. The other RCT [37] administered five sessions of bilateral high-definition tDCS to the right-and left-IFC in 33 children and adolescents with ADHD, with stimulation intensity titrated post-randomisation to .25mA (n = 11) and .5mA (n = 9) to minimise discomfort.…”