Is non-invasive brain stimulation in danger of becoming a pseudo-science?

Non-invasive methods of human brain stimulation (such as transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (TDCS)) have hit the headlines on many occasions. They are claimed to enhance cognitive abilities in healthy brain and improve symptoms in conditions as diverse as depression, tinnitus, Parkinson’s disease, anorexia, addiction etc. In fact so many claims have been made that the only common sense conclusion is that some of them are not true (or at least not as reliable as the initial reports might claim). It’s a situation in which everyone loses: the public because they no longer trust scientists, and scientists because grant panels increasingly treat the methods as snake oil and deny funding. I argue that the only way forwards is for research to provide clear neurophysiological mechanisms that account for experimental results. This is becoming true for TMS since we know how it stimulates neurones to initiate action potentials and activity at neural synapses. However, things are not so clear with TDCS since its actions on neurones in human brain are still debated even among experts. In fact, because TDCS is so cheap and easy to apply we may never be able to control the mass of unsupported random observations and claims that are made. If so the future for the method could be bleak. Is there a solution?