Follow-up effects of transcranial direct current stimulation (tDCS) for the major depressive episode: A systematic review and meta-analysis

Transcranial Direct Current Stimulation (tDCS) is an effective treatment during the acute phase of a major depressive episode (MDE), although the evidence for its follow-up efficacy is mixed. A systematic review and meta-analysis were performed. MEDLINE/PubMed, Scopus (EMBASE), Web of Science, Cochrane Library and additional sources were searched from inception to April 29, 2021. Studies that followed up adults treated with tDCS during an MDE - using (interventional) and/or not using (observational) tDCS in the follow-up period were included. The primary outcome was the Hedges' g for the follow-up depression scores. Small study effects and sources of heterogeneity were explored. 427 studies were retrieved and 11 trials (13 datasets, n = 311) were included, most presenting moderate bias. Results showed a follow-up depression improvement (k = 13, g = -0.81, 95% confidence interval [CI]: -1.28; -0.34, I-2 = 84.0%), which was probably driven by the interventional studies (k = 7, g = -1.12, 95% CI: -1.84; -0.40, I-2 = 87.1%). No predictor of response was associated with the outcome. No risk of publication bias was found. Significant between-study heterogeneity may have influenced the overall results. Our findings suggest that tDCS produces effects beyond the intervention period during MDEs. Maintenance sessions are advised in future research.

Automated summary

This study conducted a systematic review and meta-analysis on the efficacy of transcranial direct current stimulation (tDCS) during the acute phase of a major depressive episode (MDE), finding a potential improvement in depression symptoms during the follow-up period. The results suggest that tDCS may have effects beyond the intervention period and maintenance sessions are recommended for future research.