The comparative effects of anodal and cathodal trans-cranial direct current stimulation on balance and posture: A systematic review of literature and meta-analysis

Application of anodal trans-cranial direct current stimulation (a-tDCS) versus cathodal tDCS (c-tDCS) can influence the physiological results of tDCS intervention on postural control and balance in patients or healthy adults. According to the evidence, some studies demonstrated that postural control or balance is facilitated by the application of the a-tDCS more than the c-tDCS. On the other hand, some studies indicated that there were no significant differences between a-tDCS and c-tDCS. In contrast, other studies have shown a more significant effect of c-tDCS than a-tDCS on postural control and balance. This study aimed to systematically review the studies which investigated the effectiveness of a-tDCS and c-tDCS intervention on postural control and balance. The search was performed from databases in Google Scholar, PubMed, Elsevier, Medline, Ovid, and Science Direct with the keywords of balance, balance test, postural control, postural stability, postural sway, posture, postural balance, trans-cranial direct current stimulation, tDCS, neuromodulator, neurostimulation, tDCS, a-tDCS or anodal tDCS, c-tDCS or cathodal tDCS from 2000 to 2022. The results confirmed that the study population was a key factor in determining the study's findings. Data meta-analysis showed no significant differences between active tDCS and sham tDCS on postural control in healthy individuals (P > 0.05). In addition, the results indicated the efficacy of both a-tDCS over the affected motor cortex (M1) and c-tDCS over unaffected M1 as compared to sham tDCS on postural improvement in patients with stroke (P < 0.05), however, there were no differences between the two techniques on posture and balance in these patients.