A Meta-Analysis of the Effects of Transcranial Direct Current Stimulation on Anger and Aggression.

Anger and aggression are causes of significant suffering. Psychological methods to prevent and reduce anger and aggression have been partially successful; however, there is room for novel interventions, such as those informed by neuroscience. One such intervention is anodal transcranial direct current stimulation (tDCS), which involves administering a weak electrical current to the brain to stimulate cortical activity. In this meta-analysis, we synthesized 93 effect sizes from 25 sham-controlled experiments. We predicted that tDCS would reduce anger and aggression. The overall results showed no effect of tDCS on anger and aggression (Hedges' g = -0.03, CI = -0.30, 0.24). Separate meta-analyses of the dorsolateral prefrontal cortex, ventromedial prefrontal cortex, and ventrolateral prefrontal cortex showed no effects of tDCS. The meta-analysis was limited by low power in the source articles (average power = 0.33); No study reached the sufficient sample size to detect a medium effect. Thus, there is room for more well-powered research on the topic to determine whether tDCS may reduce aggression.