Blinding is compromised for transcranial direct current stimulation at 1 mA for 20 min in young healthy adults

Zsolt Turi, Gábor Csifcsák, Nya Mehnwolo Boayue, Per Aslaksen, Andrea Antal, Walter Paulus, Josephine Groot, Guy E. Hawkins, Birte Forstmann, Alexander Opitz, Axel Thielscher, Matthias Mittner

Research output: Contribution to journalArticlepeer-review

66 Scopus citations


Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation method that is frequently used to study cortical excitability changes and their impact on cognitive functions in humans. While most stimulators are capable of operating in double-blind mode, the amount of discomfort experienced during tDCS may break blinding. Therefore, specifically designed sham stimulation protocols are being used. The “fade-in, short-stimulation, fade-out” (FSF) protocol has been used in hundreds of studies and is commonly believed to be indistinguishable from real stimulation applied at 1 mA for 20 min. We analysed subjective reports of 192 volunteers, who either received real tDCS (n = 96) or FSF tDCS (n = 96). Participants reported more discomfort for real tDCS and correctly guessed the condition above chance-level. These findings indicate that FSF does not ensure complete blinding and that better active sham protocols are needed.

Original languageEnglish (US)
Pages (from-to)3261-3268
Number of pages8
JournalEuropean Journal of Neuroscience
Issue number8
StatePublished - Oct 1 2019

Bibliographical note

Funding Information:
The writing of this paper was supported by the Research Program, University Medical Center, University of Goettingen awarded to ZT. AT received support from Lundbeckfonden (R118-A11308) and Novo Nordisk Fonden by a synergy grant on Biophysically adjusted state-informed cortex stimulation (BASICS; NNF14OC0011413). This work was supported by the Northern Norway Regional Health Authority (grant no. PFP1237-15) for GC and MM.

Publisher Copyright:
© 2019 Federation of European Neuroscience Societies and John Wiley & Sons Ltd


  • active sham tDCS
  • blinding
  • double-blinding
  • placebo
  • transcranial direct current stimulation


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