Background Transcranial direct current stimulation (tDCS) has shown promising clinical results, leading to increased demand for an evidence-based review on its clinical effects. Objective We convened a team of tDCS experts to conduct a systematic review of clinical trials with more than one session of stimulation testing: Pain, Parkinson’s Disease Motor Function and Cognition, Stroke Motor Function and Language, Epilepsy, Major Depressive Disorder, Obsessive-Compulsive Disorder, Tourette Syndrome, Schizophrenia and Drug Addiction. Methods Experts were asked to conduct this systematic review according to the search methodology from PRISMA guidelines. Recommendations on efficacy were categorized into: Levels A (definitely effective), B (probably effective), C (possibly effective) or no recommendation. We assessed risk of bias for all included studies to confirm whether results were driven by potentially biased studies. Results Although most of the clinical trials have been designed as proof-of-concept trials, some of the indications analyzed in this review can be considered as definitely effective (Level A) such as depression, probably effective (Level B) such as neuropathic pain, fibromyalgia, migraine, post-operative patient-controlled analgesia and pain, Parkinson´s disease (motor and cognition), stroke (motor), epilepsy, schizophrenia and alcohol addiction. Assessment of bias showed that most of the studies had low risk of biases and sensitivity analysis for bias did not change these results. Effect sizes vary from 0.01 to 0.70 and were significant in about 8 conditions, with largest effect size being in postoperative acute pain, and smaller in stroke motor recovery (nonsignificant when combined with robotic therapy). Conclusion All recommendations listed here are based on current published Pubmed-indexed data. Despite high level of evidence in some conditions, it needs to be underscored that effect sizes and duration of effects are often limited; thus, real clinical impact needs to be further determined with different study designs.

The field of transcranial electrical stimulation (tES) has experienced significant growth in the past 15 years. One of the tES techniques leading this increased interest is transcranial direct current stimulation (tDCS). Significant research efforts have been devoted to determining the clinical potential of tDCS in humans. Despite the promising results obtained with tDCS in basic and clinical neuroscience, further progress has been impeded by a lack of clarity on international regulatory pathways. We therefore convened a group of research and clinician experts on tDCS to review the research and clinical use of tDCS. In this report, we review the regulatory status of tDCS, and we summarize the results according to research, off-label and compassionate use of tDCS in the following countries: Australia, Brazil, France, Germany, India, Iran, Italy, Portugal, South Korea, Taiwan and United States. Research use, off label treatment and compassionate use of tDCS are employed in most of the countries reviewed in this study. It is critical that a global or local effort is organized to pursue definite evidence to either approve and regulate or restrict the use of tDCS in clinical practice on the basis of adequate randomized controlled treatment trials.