Transcranial Direct Current Stimulation (tDCS) applies a current amount (dose) that is determined by the intensity of current flow, in mA, and the time of current flow, in minutes. In 2000, classic tDCS studies by Michael Nitsche used 1 mA intensity (1 mA is one thousandth of an Amp). Starting around 2006 early clinical trials by Felipe Fregni increased the current intensity to 2 mA. 2 mA has since remained the current intensity of choice for many clinical trials including a trial using the Soterix Medical tDCS LTE for depression as well as for a range of other diseases like Parkinson’s, epilepsy, schizophrenia, and anxiety.
Around 2012, Roy Hamilton at the University of Pennsylvania started testing tDCS in healthy people using a current of 1.5 mA. About 1.5 mA remains popular when tDCS is used to boost brain power and learning. As a result, current around 1.5 mA is what is found in more out-of-the-box consumer devices. But there are other research papers, such as those by Vince Clark, where 2 mA seems to be the standard.
tDCS.com could not find scientific papers where1.5 mA was compared to 2 mA. This could indicate that these two values might work about the same?
Can tDCS with a current higher than 2 mA work?
When discussing the safety of tDCS, Marom Bikson notes 2 mA (or less) is by far the most common, but that does not necessarily mean the use of slightly higher current is risky at all. Bikson actually showed 4 mA tDCS was tolerable as long as “adaptive” techniques were used. It could be that one reason clinical trials hover around 2 mA and experiments on brain boosting use around 1.5 mA is that people find these current levels comfortable.
Our own testing with devices like the ActivaDose-tDCS, the consumer version Activatek with the 4 mA option, is that for some users the “prickling” feeling at 3 mA can get pretty intense and at 4 mA some may find it too painful. However, some users just don’t seem to mind. Using “adaptive” tDCS, users may feel that the skin sensation from 2 mA and 4 mA the same, but as far as we know that it not available on any consumer device.
Bottom line: Keeping intensity around 2 mA seems standard for clinical indications and around 1.5 mA is standard for brain boosting.
What is the best session duration? 10 minutes? 20 minutes? 30 minutes? Even more? We will cover that in a later tDCS.com article. To never miss an important tDCS update, and get special tDCS promotions: join our mailing list using the signup form below.