More Evaluations Needed for Transcranial Direct Current Stimulation Efficacy in Neurodevelopmental Disorders

Mohammad Ali Salehinejad

Transcranial direct current stimulation (tDCS) is safe and partially effective in treating attention deficit/hyperactivity disorder (ADHD), autism spectrum disorder (ASD), and dyslexia.

A team, led by Mohammad Ali Salehinejad, Department of Psychology and Neurosciences, Leibniz Research Centre for Working Environment and Human Factors, provided an update on published randomized-controlled trials applying transcranial direct current stimulation in patients with ADHD, autism spectrum disorder, and dyslexia.

The Treatment

Transcranial direct current stimulation has been used to treat neurodevelopmental disorders among target groups in pediatric psychiatry, particularly to treat ADHD, autism spectrum disorder, and dyslexia.

“Over the last two decades, transcranial direct current stimulation has been exponentially applied in humans for studying and modifying brain physiology that underlies cognition, as well as for improving symptoms in clinical populations that suffer from plasticity-related symptoms/deficits,” the authors wrote. “Yet, the number of currently available studies in children and adolescents is limited compared to adults.”

Identifying Literature

In the study, the investigators identified 35 randomized controlled trials investigating the effects of transcranial direct current stimulation on pediatric patients with ADHD (n = 17), autism spectrum disorder (n = 11), and dyslexia (n = 7).

The results show prefrontal anodal transcranial direct current stimulation is more effective in treating ADHD compared to stimulation of the right inferior frontal gyrus.

Prefrontal anodal transcranial direct current stimulation was similarly effective for improving behavioral problems for pediatric patients with autism spectrum disorder.

For patients with dyslexia, stimulating temporoparietal regions was the most common and effective protocol.

All of the studies involving patients with autism spectrum disorder and dyslexia showed an improvement in at least 1 of the outcome variables using transcranial direct current stimulation.

In addition, 64.7% (n = 11) of studies involving patients with ADHD found a similar effect in at least 1 of the outcome variables.

Approximately 88% (n = 16) of all studies with a multi-session design in 3 disorders found a significant improvement in 1 or all outcome variables following transcranial direct current stimulation intervention.

Randomized, double-blind, controlled trials consisted of around 70.5% of transcranial direct current stimulation studies for ADHD, compared to 36.3% for autism spectrum disorder and 57.1% for dyslexia.

Transcranial direct current stimulation was also deemed safe with no reported serious side effects in 6587 sessions conducted on 745 pediatric patients.

“tDCS was found safe and partially effective. For evaluation of clinical utility, larger randomized controlled trials with a double-blind design and follow-up measurements are required,” the authors wrote. “Titration studies that systematically evaluate different stimulation intensities, duration, and electrode placement are lacking.”

Limitations

There were some limitations involved in the study.

For example, the quality of established evidence in the review was low due to small sample sizes, a lack of long-term follow-ups, and several risks of bias. The heterogenous stimulation parameters in ADHD studies and the low number of double-blind randomized controlled trials in autism spectrum disorders were also limitations.

The study, “A systematic review of randomized controlled trials on efficacy and safety of transcranial direct current stimulation in major neurodevelopmental disorders: ADHD, autism, and dyslexia,” was published online in Brain and Behavior.