Non-Invasive Brain Stimulation for Autism Spectrum Disorder: A Review of Stimulation Parameters and Outcomes

Introduction: Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by difficulties in social communication, repetitive behaviors, and limited interests. Non-invasive brain stimulation refers to a collection of methods that regulate brain activity without resorting to surgical procedures or invasive interventions. The two most prevalent forms of non-invasive brain stimulation are transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS). TMS employs potent magnetic fields to induce electrical currents in precise cerebral regions, whereas tDCS involves the application of mild electrical currents to the scalp through electrodes. Therefore, a systematic review is performed to assess the effectiveness and achievement of non-invasive brain stimulation (NIBS) for ASD through completed randomized controlled trials (RCTs).

Methods: A thorough search was conducted on PubMed and Google Scholar databases, where relevant studies were meticulously identified and retrieved. Randomized controlled trials employing sham controls to investigate the impact of TMS or tDCS on ASD. Data on study details, interventions, parameters, and outcomes were extracted by two independent researchers into a standardized table.

Results: A total of 25 RCTs with 626 participants were included. Overall, studies indicate favorable impacts of NIBS on social communication, repetitive behaviors, and cognitive functions in ASD. The risk of bias is minimal because of the predominant inclusion of randomized controlled trials with blinding and sham control. Notably, no substantial adverse effects were observed. However, some studies have shown mixed results.

Conclusion : The data and evidence analyzed and incorporated into this review form a compelling foundation for employing NIBS to alleviate symptoms in individuals with ASD. To delve deeper into the precise effectiveness of NIBS for patients with ASD, it is imperative to undertake extensive large-scale multicenter randomized double-blind controlled trials, accompanied by pertinent follow-up observations. Current evidence tentatively supports NIBS for improving ASD symptoms, but larger controlled trials with long-term follow-up are needed.