Transcranial Direct Current Stimulation for the Treatment of Depression: a Review of the Candidate Mechanisms of Action

Purpose of Review: Numerous studies published in the last 10 years indicate that repeated administration of prefrontal transcranial direct current stimulation (tDCS) is a potential effective treatment for major depressive disorder (MDD). However, the mechanisms of action are unclear and methods of patient selection for clinical trials are limited. This review seeks to examine the potential neural and cognitive mechanisms of action of tDCS in the treatment of MDD, to aid patient selection for future clinical trials. Recent Findings: Cognitive measures of tDCS efficacy in the treatment of MDD have begun to be examined over the past 5 years. Baseline measures of working memory and letter fluency have been shown to predict treatment response. In addition, tDCS reduced cognitive deficits induced by stress, suggesting a protective mechanism. Summary: Baseline measures of working memory and letter fluency may aid patient selection in future clinical trials of tDCS. In addition, reduction of stress responsivity may be a key mechanism of action for tDCS in clinical groups and merits further investigation, acutely and post-treatment. © 2018, Springer International Publishing AG, part of Springer Nature.