Effects of Transcranial Direct Current Stimulation (tDCS) for Auditory Hallucinations: A Systematic Review.

Background: Transcranial direct current stimulation (tDCS) is a non-invasion brain stimulation, which has been suggested as a safe and promising treatment for auditory hallucinations, however, no systematic review has been conducted to evaluate the effects of tDCS on auditory hallucinations (AH).

Objective: To investigate the efficacy and safety of tDCS for auditory hallucinations among patients with schizophrenia.

Methods: We searched relevant randomized controlled trials (RCTs) from PubMed, EMBASE, the Cochrane Library, Chinese National Knowledge Infrastructure, Chongqing VIP database for Chinese Technical Periodicals, WANFANG DATA, Chinese Biological Medical Literature Database, and Taiwan Electronic Periodical Services (TEPS) before February 13, 2016. Studies were selected based on pre-defined inclusion and exclusion criteria. The quality of each included study was assessed by the risk of bias table. The levels of evidence of primary outcomes were evaluated using GRADE criteria. Data synthesis was conducted using RevMan 5.3.

Results: 304 papers were screened. Finally, three studies with a combined sample size of 87 patients were included in the meta-analysis. Two studies were classified as having 'low risk of bias', one study was classified as having 'unclear'. Inconsistent results and the overall level of evidence of primary outcome was graded as 'low'.

Conclusions: The sample sizes of the published studies were small and the results were inconsistent. We could not draw any strong conclusions from these trials. Further high quality RCTs with large sample sizes are needed to assess the efficacy of tDCS for auditory hallucinations in patients with schizophrenia.