title: Use of transcranial direct current stimulation for the treatment of auditory hallucinations of schizophrenia - a systematic review.
abstract: BACKGROUND
  Auditory hallucinations are defined as experiences of auditory perceptions in the absence of a provoking external stimulus. They are the most prevalent symptoms of schizophrenia with high capacity for chronicity and refractoriness during the course of disease. The transcranial direct current stimulation (tDCS) - a safe, portable, and inexpensive neuromodulation technique - has emerged as a promising treatment for the management of auditory hallucinations.
  
  
  OBJECTIVE
  The aim of this study is to analyze the level of evidence in the literature available for the use of tDCS as a treatment for auditory hallucinations in schizophrenia.
  
  
  METHODS
  A systematic review was performed, searching in the main electronic databases including the Cochrane Library and MEDLINE/PubMed. The searches were performed by combining descriptors, applying terms of the Medical Subject Headings (MeSH) of Descriptors of Health Sciences and descriptors contractions. PRISMA protocol was used as a guide and the terms used were the clinical outcomes ("Schizophrenia" OR "Auditory Hallucinations" OR "Auditory Verbal Hallucinations" OR "Psychosis") searched together ("AND") with interventions ("transcranial Direct Current Stimulation" OR "tDCS" OR "Brain Polarization").
  
  
  RESULTS
  Six randomized controlled trials that evaluated the effects of tDCS on the severity of auditory hallucinations in schizophrenic patients were selected. Analysis of the clinical results of these studies pointed toward incongruence in the information with regard to the therapeutic use of tDCS with a view to reducing the severity of auditory hallucinations in schizophrenia. Only three studies revealed a therapeutic benefit, manifested by reductions in severity and frequency of auditory verbal hallucinations in schizophrenic patients.
  
  
  CONCLUSIONS
  Although tDCS has shown promising results in reducing the severity of auditory hallucinations in schizophrenic patients, this technique cannot yet be used as a therapeutic alternative due to lack of studies with large sample sizes that portray the positive effects that have been described.
authors.affiliation: Dynamics of Neuromusculoskeletal System Laboratory, Bahiana School of Medicine and Public Health.
authors.forename: Pedro H
authors.initials: PH
authors.lastname: Pondé
authors.affiliation: Postgraduate Program in Interactive Process of Organs and Systems, Federal University of Bahia, Salvador, Bahia, Brazil.
authors.forename: Eduardo P
authors.initials: EP
authors.lastname: de Sena
authors.affiliation: Laboratory for Neuropsychiatry and Neuromodulation and Transcranial Magnetic Stimulation Clinical Service, Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Joan A
authors.initials: JA
authors.lastname: Camprodon
authors.affiliation: Postgraduate Program in Interactive Process of Organs and Systems, Federal University of Bahia, Salvador, Bahia, Brazil.
authors.forename: Arão Nogueira
authors.initials: AN
authors.lastname: de Araújo
authors.affiliation: Scientific Training Center Department, School of Medicine of Bahia, Federal University of Bahia, Salvador, Bahia, Brazil.
authors.forename: Mário F
authors.initials: MF
authors.lastname: Neto
authors.affiliation: Neuromodulation Center, Spaulding Rehabilitation Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Melany
authors.initials: M
authors.lastname: DiBiasi
authors.affiliation: Functional Electrostimulation Laboratory, Biomorphology Department; Postgraduate Program on Medicine and Human Health, School of Medicine, Federal University of Bahia, Salvador, Bahia, Brazil.
authors.forename: Abrahão Fontes
authors.initials: AF
authors.lastname: Baptista
authors.affiliation: Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Lidia Mvr
authors.initials: LM
authors.lastname: Moura
authors.affiliation: Postgraduate Program in Interactive Process of Organs and Systems, Federal University of Bahia, Salvador, Bahia, Brazil; Laboratory for Neuropsychiatry and Neuromodulation and Transcranial Magnetic Stimulation Clinical Service, Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA; Functional Electrostimulation Laboratory, Biomorphology Department; Center for Technological Innovation in Rehabilitation, Federal University of Bahia; Bahia State Health Department (SESAB), Salvador, Bahia, Brazil.
authors.forename: Camila
authors.initials: C
authors.lastname: Cosmo
keywords: auditory hallucinations; non-invasive brain stimulation; schizophrenia; tDCS