Controlled investigation of transcranial direct-current stimulation (tDCS) for treating neuropsychiatric disorders or for neurorehabilitation should not be confused with improvised devices or practices that apply electricity to the brain without reference to established protocols (see Nature 498, 271-272; 2013). Unorthodox technologies and applications must not be allowed to distort the long-term validation of tDCS.

Experimentation outside established and tested norms may put subjects at risk. In tDCS, the delivered dose of electrical brain stimulation (defined by the waveform and intensity applied) and the electrode size, number and position are all crucial. Safe and effective dose ranges have been established in clinical trials. Patients receiving tDCS do so in a controlled environment, under guidance from institutional ethics review boards and with strict criteria for patient inclusion.

Meddling with the tDCS dose is potentially as dangerous as tampering with a drug’s chemical composition. Painstaking efforts by researchers to understand the risks and benefits of tDCS should never be interpreted as encouraging such practices.