Name: Yngve Dahl Title: Transcranial Direct Current Stimulation for the Treatment of Depression – A Systematic Review. Supervisor: Stein Andersson Objective: Transcranial direct current stimulation (tDCS) is a relatively new form of non-invasive brain stimulation. It has quickly emerged as a potential treatment for a number of neuropsychiatric conditions, including depression. Depression is a condition with a significant societal impact and a high personal burden of disease, with a substantial proportion of patients not responding adequately to traditional treatment regimens. Consequently, novel treatment methods for depression should be explored to determine their potential efficacy.The aim of this thesis was to explore the current state of tDCS research into depression, the evidence surrounding its potential efficacy and highlight the methodological challenges still apparent in many of the studies. Method: The available literature was systematically reviewed, focusing on open label and randomized, sham controlled trials. 7 RCTs and 5 open label studies were included in the systematic review. Furthermore, a selection of reviews and meta-analyses were also reviewed in order to demonstrate areas of convergence and divergence within the field. Discussion: Qualitatively, there was a substantial amount of heterogeneity in the included studies. Samples sizes and clinical characteristics differed, aspects of stimulation protocols were different and the degree of treatment resistance varied greatly. This may partly account for the mixed results observed in tDCS treatment of depression. These differences can also be observed in the results of the meta-analyses, where differing conclusions were drawn. Which groups of depressed patients will benefit the most from tDCS treatment is not known at the moment. Conclusion: While the results have been mixed, tDCS appears to have a potential anti-depressant effect. It has produced statistically significant results in a number of studies, as well as clinically meaningful results in terms of many participants acheieving both treatment response and remission. This is supported by several meta-analyses.