Efficacy of Transcranial Direct Current Stimulation for Chronic Non-Specific Low Back Pain: A Systematic Review and Meta-Analysis

Background: Chronic non-specific low back pain (CNSLBP) is highly disabling, and the efficacy of transcranial direct current stimulation (tDCS) remains uncertain. This systematic review and meta-analysis evaluated the effects of standalone and combined tDCS on pain and functional disability in adults with CNSLBP, with secondary comparisons between M1 and DLPFC stimulation. Methods: PubMed, Web of Science, Science Direct, China National Knowledge Infrastructure, Chinese Quarterly Virtual Information Platform, and Wanfang Data were searched up to February 2026. Randomized controlled trials of standalone or combined tDCS in adults with CNSLBP were included. Meta-analyses assessed pain intensity and functional disability, with subgroup analyses comparing stimulation targets and meta-regression exploring protocol parameters. Evidence certainty was evaluated using GRADE, and the protocol was registered with PROSPERO (CRD420261341095). Results: Meta-analysis of 17 trials showed that standalone tDCS did not significantly reduce pain intensity, whereas tDCS combined with peripheral interventions yielded a significant analgesic effect, and anodal stimulation over M1 significant reduced pain intensity. However, neither standalone nor combined tDCS significantly improved functional disability, subgroup differences between M1 and DLPFC were non-significant, and meta-regression identified no significant moderators. Descriptive findings showed potential benefits of tDCS for pain catastrophizing and postural control, with mild adverse events. Conclusions: Moderate-certainty evidence suggests that standalone tDCS is unlikely to provide clinically meaningful analgesia for CNSLBP. Low-certainty evidence indicates that anodal M1 tDCS combined with structured peripheral interventions, particularly exercise, may produce analgesic benefits, but this finding requires cautious interpretation.