Effectiveness of Low Frequency Noninvasive Brain Stimulation Therapy for Improving Neuropsychological and Neurophysiological Functions: A Systematic Review

Introduction. Cranial electrotherapy stimulation (CES) is a technique used to address various mental disorders symptoms. However, it is recently concluded that the quality of clinical trials involving CES is not standardized and lacks sufficient evidence to support its use for improving mental health. The purpose of this study was to undertake a systematic examination of evidence of CES in improving mental health. Method. From inception to April 2022, systematic review was conducted using electronic databases MEDLINE (accessed via PubMed), CENTRAL (Cochrane Library Central Register of Controlled Trials), and Web of Science to retrieve relevant studies. Methodology of all the identified randomized controlled trials (RCTs) was assessed using an 11-point PEDro scale by two independent reviewers. Results. Sixteen RCTs were identified to be relevant and their characteristics were evaluated. Thirteen studies concluded CES has favorable effect on variety of mental disorders, particularly on anxiety and depressed symptoms in varied groups. Conclusions. While these positive effects were observed, limitations included insufficient detail about existing treatments, lack of using standardized objective outcome measures for quantifying mental health dysfunction, and uneven representation of CES limiting the generalizability and making it difficult to carry out the pooled quantification and meta-analysis. Despite its shortcomings, literature suggests that CES warrants more research.