Abstract
BACKGROUND: Auditory hallucinations are a hallmark symptom of schizophrenia, with approximately 70% of patients endorsing hallucinations in their lifetime. Of these, 25–30% of patients continue to experience auditory hallucinations despite adequate antipsychotic treatment. In recent years there has been growing interest in adjunct non-invasive neuromodulation therapy for mental health disorders, particularly for the alleviation of medication resistant symptoms by tempering atypical neural activity. Transcranial Direct Current Stimulation (tDCS) is an especially low-risk method that has attracted significant interest for potential treatment of refractory auditory hallucinations. TDCS uses surface electrodes placed on the scalp to administer a gentle electrical current intended to modulate the excitability of underlying cortical regions. With this new area of research quickly widening, there is demand for a more up-to-date understanding of the effects of tDCS on auditory hallucinations in schizophrenia. METHODS: To address this need, the authors undertook a systematic review and meta-analysis of the literature base in PubMed by using search terms related to schizophrenia, tDCS, and auditory hallucinations. The search, conducted in November of 2018, garnered 54 papers which were screened and reduced to 13 for review. RESULTS: Preliminary analyses suggest a significant large negative relationship between tDCS and the incidence of auditory hallucinations in schizophrenia when examining studies with repeated measures designs (d=-1.37, CI: -1.70, -1.03) and a non-significant medium effect on auditory hallucinations in studies with sham-controlled designs (d=-0.53, CI: -1.70, -1.03). DISCUSSION: These data suggest a very promising avenue for intervention with relatively no reported adverse effects when compared with sham. Additionally, the authors provide a commentary on the methodological approaches used and discuss directions for future inquiry.