IntroductionTranscranial direct current stimulation (tDCS) is a promising neuromodulation method that has, for example, been used to treat depression. Nevertheless, the adverse effects of tDCS and the validity of the current standard tDCS sham protocols have received limited attention.ObjectivesTo evaluate the extent and types of tDCS adverse effects and to assess the reliability of sham stimulation as a control procedure for tDCS in a double-blind setting.AimsTo compare adverse effects between tDCS and sham stimulation groups, and to determine how well the participants and the experimenter are able to distinguish tDCS from sham stimulation.MethodsA sample of healthy volunteers received a 20-minute session of either tDCS (n = 41; 2 mA) or sham stimulation (n = 41; ramp up 15 s, ramp down 15 s; no current in between). The anode was placed over F3 and cathode over F4. Both the participants and the experimenter reported immediate adverse effects and the perceived likelihood for the participant to receive tDCS. Analyses were conducted using the Mann–Whitney U-test.ResultsThe tDCS group reported more erythema compared with the sham group (P = 0.016, Cohen's D = 0.444). No other significant differences in adverse effects were observed. In the tDCS group, both the participants (P = 0.034, Cohen's D = 0.612) and the experimenter (P = 0.006, Cohen's D = 0.674) reported a higher perceived likelihood of the participant receiving tDCS than in the sham group.ConclusionstDCS has only modest adverse effects. Nevertheless, the current standard sham protocol appears insufficient.Disclosure of interestThe authors have not supplied their declaration of competing interest.

Fig. 1. Skin lesions of the two participants on different days following stimulation.

No abstract

Background: Transcranial direct current stimulation (tDCS), a putative treatment for depression, has been proposed to affect peripheral metabolism. Metabolic products from brain tissue may also cross the blood-brain barrier, reflecting the conditions in the brain. However, there are no previous data regarding the effect of tDCS on circulating metabolites.Objective: To determine whether five daily sessions of tDCS modulate peripheral metabolites in healthy adult men.Methods: This double-blind, randomized controlled trial involved 79 healthy males (aged 20-40 years) divided into two groups, one receiving tDCS (2 mA) and the other sham stimulated. The anode was placed over the left dorsolateral prefrontal cortex and the cathode over the corresponding contralateral area. Venous blood samples were obtained before and after the first stimulation session, and after the fifth stimulation session. Serum levels of 102 metabolites were determined by mass spectrometry. The results were analysed with generalised estimating equations corrected for the family-wise error rate. In addition, we performed power calculations estimating sample sizes necessary for future research.Results: TDCS-related variation in serum metabolite levels was extremely small and statistically non-significant. Power calculations indicated that for the observed variation to be deemed significant, samples sizes of up to 11,000 subjects per group would be required, depending on the metabolite of interest.

No abstract