Attention Maintenance Improved With Direct Current Stimulation in Kids With ADHD

Overall symptoms of children and adolescents with attention-deficit/hyperactivity disorder (ADHD) are not significantly alleviated with high-definition transcranial direct current stimulation (HD-tDCS). However there may be significant improvements in the cognitive measures of attention maintenance. The findings were published in Frontiers in Psychiatry.

Researchers sought to test their hypothesis that clinical symptoms, impulse control difficulties, and emotion processing in children and adolescents with ADHD could show improved performance on cognitive tasks with treatment of HD-tDCS of the right orbital frontal cortex (OFC).

They conducted a randomized, sham-controlled trial of high-definition transcranial direct current stimulation on the right orbital frontal cortex in children and adolescents (aged 8 to 18 years) with ADHD who visited the general outpatient department and the children’s outpatient department of the Zhenjiang Mental Health Center (The Fifth People’s Hospital of Zhenjiang City), Zhenjiang, Jiangsu, China between March 2020 and November 2021.

They recruited and randomly assigned 56 patients with ADHD, of whom 47 completed each session and evaluation. There were 28 individuals allocated to the HD-tDCS group who received real stimulation and 28 individuals allocated to the sham group who received sham stimulation. Each group had 2 individuals who discontinued treatment and the HD-tDCS group lost 2 to follow-up and the sham group lost 3 to follow-up. Reasons for loss included inconvenience, uncomfortable stimulation of the head, and no treatment effect. All children were right-handed and of Chinese Han origin.

Individuals with metal device implants, skull defects, intracranial hypertension, history of brain trauma, epilepsy, and other serious neurologic, circulatory, endocrine, and other physical diseases; audio-visual impairments and color blindness, color weakness, or narrow-angle glaucoma were excluded as were individuals who were recently treated for ADHD with any medication or who received other brain stimulation.

A 1.0mA anode current was applied to the right OFC, the HD-tDCS group received real stimulation (10 girls, 14 boys; 11.29±2.51 years of age) and the sham group received sham stimulation (10 girls, 13 boys; 11.74±2.59 years of age) in treatment for 10 sessions. Researchers noted there were no significant differences between the 2 groups in sex, age, educational years, total IQ, course of disease, age of onset, whether they came from a single-parent family, and ADHD type (P >.05).

Cognitive effect was evaluated by the Integrated Visual and Auditory Continuous Performance Test (IVA-CPT), the Stroop Color and Word Test (Stroop), and the Tower of Hanoi (TOH). ADHD symptom assessment (the SNAP-IV Rating Scale and the Perceived Stress Questionnaire [PSQ]) was carried out before treatment, after the fifth and tenth stimuli, and at the sixth week after the end of all stimulation.

Researchers found the mean visual and auditory reaction times by IVA-CPT, the interference RT of Stroop Color and Word, the number of completed steps of TOH, SNAP-IV score, and PSQ score did not change with intervention time before and after treatment (P <.0031). They noted that compared to the sham group after the fifth intervention, tenth intervention, and the sixth week of intervention follow-up, the integrated visual and audiovisual commission errors and the TOH completion time results of the HD-tDCS group were significantly decreased.

Visual and audiovisual commission errors reflect the inhibition ability of impulse in attention-maintaining tasks and inhibition-control tasks. Tasks are created to be mildly boring to produce commission errors through trial sets requiring not responding.

The goal of the TOH is to move stacked disks 1 at a time from a starting position to a target position, arranged in a pyramid form on the target position without ever placing a larger disk on top of a smaller disk. The time of accomplishment of the TOH improved but the number of steps required for accomplishment did not improve. Researchers suggested that real tDCS improves attention maintenance, and participants need to increase sustained attention to complete tasks without distraction.

Significant study limitations include underpowered sample size, high depigmentation rate, impatience of participants during stimulation, lack of age stratification, inability to distinguish treatment effects among different ADHD subtypes, unaccounted for learning effect and repetition effect, and no crossover experimental design.

Researchers concluded their study “draws cautious conclusions that HD-tDCS does not significantly alleviate the overall symptoms of patients with ADHD but leads to significant improvements in the cognitive measures of attention maintenance.” They wrote, “tDCS cannot be recommended as an alternative neurotherapy for ADHD yet.”