Background: Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder manifesting as lifelong deficits in social communication and interaction, as well as restricted repetitive behaviors, interests and activities. While there are no specific pharmacological or other physical treatments for autism, in recent years repetitive Transcranial Magnetic Stimulation (rTMS), a technique for non-invasive neuromodulation, has attracted interest due to potential therapeutic value. Here we report the results of a systematic literature review and meta-analysis on the use of rTMS to treat ASD.Methods: We performed a systematic literature search on PubMed, Web of Science, Science Direct, Bielefeld Academic Search, and Educational Resources Information Clearinghouse. Search terms reflected diagnoses and treatment modalities of interest. Studies reporting use of rTMS to treat core ASD or cognitive symptoms in ASD were eligible. Two researchers performed article selection and data extraction independently, according to PRISMA guidelines. Changes in ASD clinical scores or in cognitive performance were the main outcomes. Random effects meta-analysis models were performed.Results: We found 23 eligible reports, comprising 4 case-reports, 7 non-controlled clinical trials, and 12 controlled clinical trials, comparing the effects of real TMS with waiting-list controls (n = 6) or sham-treatment (n = 6). Meta-analyses showed a significant, but moderate, effect on repetitive and stereotyped behaviors, social behavior, and number of errors in executive function tasks, but not other outcomes. Most studies had a moderate to high risk of bias, mostly due to lack of subject- and evaluator-blinding to treatment allocation. Only 5 studies reported stability of these gains for periods of up 6 months, with descriptions that improvements were sustained over time.Conclusions: Existing evidence supports that TMS could be useful to treat some dimensions of ASD. However, such evidence must be regarded with care, as most studies did not adequately control for placebo effects. Moreover, little is known regarding the most effective stimulation parameters, targets, and schedules. There is an urgent need for further randomized, double-blind, sham-controlled trials, with adequate follow-up periods, to test the efficacy of transcranial magnetic stimulation to treat these disorders. Available evidence must be regarded as preliminary and insufficient, at present, to support offering TMS to treat ASD.

Autistic spectrum disorders (ASD) are a group of neurodevelopmental disorders that manifest as deficits in social communication and interaction, and restricted, repetitive behaviors and interests. ASD affect at least 1% of the population and are associated with lifelong disability and early death. There are no effective biological treatments for ASD, although non-invasive neuromodulation has sparked great interest as a possibly useful therapeutic approach. Here, we present preliminary results of a systematic review on the effectiveness of transcranial magnetic stimulation (TMS) in ASD treatment. Using appropriate syntax we searched Pubmed, Web of Science, Science Direct, and Educational Resources Information Clearinghouse. Following standard PRISMA statement (Preferred Reporting Items for Systematic Reviews and Meta-analyses) procedures, we selected 12 eligible studies, comprising four controlled and four uncontrolled trials on the effects of TMS on ASD core symptoms, and 9 controlled and three uncontrolled trials on TMS effects on cognitive performance in ASD. The 12 studies totaled 233 subjects. Although combined effect sizes favor TMS in all fours groups of studies, conclusions are limited by the high study heterogeneity. Furthermore, only three of the controlled studies used sham TMS as the control intervention, and only two studies followed up the therapeutic effects after the last TMS session. Side effects, none of them serious, occurred in 6.4% of treated subjects. Our main conclusion is that there is currently little evidence that sustains the commercial offer of TMS for treating ASD. Better-designed studies are badly needed to fully elucidate the role of TMS in the treatment of ASD.Disclosure of interestThe authors have not supplied their declaration of competing interest.