Not recommended; early promise is fading fast as trial methods improve Transcranial direct current stimulation (tDCS) is a form of non-invasive brain stimulation that delivers low intensity direct current stimulation to the brain through electrodes applied to the skin over the target area. It has been found to modulate cortical excitability at the target site leading some researchers to investigate it as a possible treatment for chronic pain and a host of other conditions. tDCS has clear appeal; it is cheap, relatively easy to use, and seems to be safe. In a linked article, Luedtke and colleagues (doi:10.1136/bmj.h1640) report the results of a randomised controlled trial of transcranial direct current stimulation for chronic low back pain.1 The motor cortex is the most common target of brain stimulation for chronic pain. Based largely on studies of invasive epidural stimulation of the motor cortex, researchers hypothesised that tDCS might reduce pain by modulating activity in cortical and subcortical areas of the brain involved in pain processing and by facilitating descending inhibitory mechanisms.2 3 4 As the experience of pain is ultimately generated by …