Transcranial direct cranial stimulation (tDCS) is a promising non-pharmacological intervention for treating major depressive disorder (MDD). However, results from randomized controlled trials (RCTs) and meta-analyses are mixed. Our aim was to assess the efficacy of tDCS as a treatment for MDD. We performed a systematic review in Medline and other databases from the first RCT available until January 2014. The main outcome was the Hedges' g for continuous scores; secondary outcomes were the odds ratio (ORs) to achieve response and remission. We used a random-effects model. Seven RCTs (n = 259) were included, most with small sample sizes that assessed tDCS as either a monotherapy or as an add-on therapy. Active vs. sham tDCS was significantly superior for all outcomes (g = 0.37; 95% CI 0.04-0.7; ORs for response and remission were, respectively, 1.63; 95% CI = 1.26-2.12 and 2.50; 95% CI = 1.26-2.49). Risk of publication bias was low. No predictors of response were identified, possibly owing to low statistical power. In summary, active tDCS was statistically superior to sham tDCS for the acute depression treatment, although its role as a clinical intervention is still unclear owing to the mixed findings and heterogeneity of the reviewed studies. Further RCTs with larger sample sizes and assessing tDCS efficacy beyond the acute depressive episode are warranted.

We reviewed trigeminal nerve stimulation (TNS) and transcutaneous vagus nerve stimulation (tVNS). All techniques have shown preliminary promising results, although the results are mixed. Method: We performed a systematic review of the Medline and Embase databases, with no constraint to dates, through June 2013. The keywords were [(1) trigeminal nerve stimulation OR (2) cranial nerve OR (3) trigemin* OR (4) transcutaneous VNS OR (5) transcutaneous cranial nerve stimulation] and (6) mental disorders. Results: We included four preclinical and clinical five studies on TNS. All clinical data were based on open-label studies with small samples, which diminished the external validity of the results, thus reflecting the modest impact of TNS in current clinical practice. Of the tVNS clinical trials, three assessed physiological features in healthy volunteers, and one examined patients with epilepsy. Conclusion: TNS and tVNS improve treatment of particular neuropsychiatric disorders such as depression.Keywords: transcutaneous nerve stimulation, trigeminal stimulation, neuropsychiatric disorders. RESUMO O uso de estimulação de nervos cranianos de maneira transcutânea tem sido uma estratégia em desenvolvimento recente. Diferentes estudos apontam para resultados clínicos favoráveis no tratamento de diferentes quadros neuropsiquiátricos. Método: Revisão sistemática da literatura com base nas bibliotecas eletrônicas Medline e Embase, sem restrição de data inicial, até agosto de 2013. Os termos de busca utilizados foram [(1) trigeminal nerve stimulation OR (2) cranial nerve OR (3) trigemin* OR (4) transcutaneous VNS OR (5) transcutaneous cranial nerve stimulation] and (6) mental disorders. Resultados: Incluímos quatro estudos pré-clinicos e cinco estudos clínicos abordando estimulação do nervo trigêmeo. Todos os estudos foram abertos, com pequenas amostras, o que reduz a validade externa dos dados, refletindo a ainda incipiente atuação da técnica, apesar de promissora. Considerando-se a estimulação do nervo vago, três artigos avaliaram aspectos fisiológicos em voluntários saudáveis e um artigo estudou pacientes com epilepsia. Conclusão: As estratégias de estimulação transcutânea de nervos cranianos, apesar de incipiente, tem demonstrado resultados clínicos favoráveis no tratamento de distúrbios neuropsiquiátricos.Palavras-chave: estimulação transcutânea de nervos cranianos, estimulação do nervo trigêmeo, distúrbios neuropsiquiátricos.

Transcranial magnetic stimulation active was superior to sham stimulation for the amelioration of OCD symptoms. Trials had moderate heterogeneity results, despite different protocols of stimulation used. Further RCTs with larger sample sizes are fundamentally needed to clarify the precise impact of TMS in OCD symptoms.

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Although recent clinical studies using transcranial direct current stimulation (tDCS) for schizophrenia showed encouraging results, several tDCS montages were employed and their current flow pattern has not been investigated. We performed a systematic review to identify clinical tDCS studies in schizophrenia. We then applied computer head modeling analysis for prediction of current flow. Out of 41 references, we identified 12 relevant studies. The most employed montage was anode and cathode over the left dorsolateral prefrontal and temporoparietal cortex, respectively. Computational model analysis predicted activation and under-activation under the anode and the cathode, respectively, occurring in areas respectively associated with negative and positive symptoms. We also identified tDCS-induced electrical currents in cortical areas between the electrodes (frontoparietal network) and, to a lesser extent, in deeper structures involved in schizophrenia pathophysiology. Mechanisms of tDCS effects in schizophrenia and the usefulness of computer modeling techniques for planning tDCS trials in schizophrenia are discussed.

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