Efficacy and acceptability of transcranial direct current stimulation for treating depression: A meta-analysis of randomized controlled trials

•27 RCTs with 1204 depressed patients were included in this meta-analysis.•Active tDCS was superior to sham tDCS in modulating depressive symptoms.•The response and remission rates were comparable between active- and sham-tDCS.•A 2-mA stimulation current and 30-min tDCS session may augment the efficacy. Transcranial direct current stimulation (tDCS) is a promising nonpharmacological intervention for treating depression. We aimed to provide an updated meta-analysis assessing the anti-depressant efficacy of tDCS. We searched the literature from the first available date to 30 December 2020 to identify relevant randomized controlled trials (RCTs). 27 RCTs (N = 1204 patients, 653 in active tDCS and 551 in sham tDCS) were included. Active tDCS was superior to sham tDCS (g = 0.46, 95 % CI 0.15−0.76) in modulating depressive symptoms measured by depression rating scales. Active tDCS was also superior to sham tDCS in reducing response and remission rates, but these differences did not reach statistically significant levels (ORresponse = 1.75, 95 % CI 0.85–3.58; ORremission = 1.29, 95 % CI 0.59–2.83). The two groups had comparable dropout rates (OR = 1.28, 95 % CI 0.62–1.64). For treatments of depressive episodes, tDCS may be efficacious. Specific tDCS parameters (e.g., a 2-mA stimulation current and 30-min sessions) and clinical characteristics (e.g., antidepressant-free) may augment the treatment efficacy of tDCS.