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

Eur J Neurosci. 2019 Oct;50(8):3261-3268. doi: 10.1111/ejn.14403. Epub 2019 Apr 8.


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.

Keywords: active sham tDCS; blinding; double-blinding; placebo; transcranial direct current stimulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Awareness*
  • Double-Blind Method
  • Female
  • Humans
  • Male
  • Pain
  • Perception
  • Transcranial Direct Current Stimulation / adverse effects*
  • Transcranial Direct Current Stimulation / methods
  • Young Adult