Direct-current stimulation: brain therapy, or placebo enhancer?

Elif Batuman, for the New Yorker:

This was my first experience of transcranial direct-current stimulation, or tDCS—a portable, cheap, low-tech procedure that involves sending a low electric current (up to two milliamps) to the brain. Research into tDCS is in its early stages. A number of studies suggest that it may improve learning, vigilance, intelligence, and working memory, as well as relieve chronic pain and the symptoms of depression, fibromyalgia, Parkinson’s, and schizophrenia.


The precise physical mechanism of tDCS remains mysterious. The electric current used is too low to cause resting neurons to fire. Instead, it seems to make neurons more or less likely to fire, by changing the electrical potential of nerve-cell membranes. In other words, although tDCS can’t create new neural activity, it can enhance or reduce existing activity.


Few claims about tDCS are free from controversy. In the past few months, Jared Horvath, a fourth-year doctoral student at the University of Melbourne, published two meta-analyses of hundreds of studies, in which he claims to have found no evidence of either physiological changes to the brain or of cognitive effects from tDCS.

And, finally, I found this bit both interesting and funny:

The implication of placebo is extremely powerful: What if the body knows, in some sense, how to heal itself, and it’s just a matter of triggering that knowledge? Schambra suspects tDCS may not merely trigger the placebo effect, as all treatments do, but actually amplify it. In other words, in a controlled tDCS study, both active and sham groups get a placebo effect, but the active group may get a bigger effect.

So, the jury is out. On the one hand, what seems to help, helps. On the other hand, we should have a better understand of what’s actually providing help, and how it works. In the meantime, it’s at least an interesting series of anecdotes.