Neuroscientists cautioned patients about the dangers of self-administered transcranial direct current stimulation (tDCS) in an open letter published July 7 in Annals of Neurology. “We perceive an ethical obligation to draw the attention of both professionals and ‘do it yourself’ (DIY) users to some of these issues,” said Michael D. Fox, MD, PhD, Assistant Professor of Neurology at Harvard Medical School in Boston. The open letter, written by four neuroscientists and signed by 39 colleagues, addresses several less commonly recognized complications of self-administered brain stimulation.
Noninvasive electrical brain stimulation may help ameliorate symptoms of anxiety and depression; however, neuroscientists say that much about this technique remains unknown and could present potential risks for DIY users. “We have never formally studied tDCS at the frequencies many DIY users experiment with—for example, stimulating daily for months or longer. Because we know that stimulation from just a few sessions can be quite lasting, we infer that changes induced by these protocols may be even more so,” said Dr. Fox.
A further consideration is that tDCS affects more of the brain than people may think. Although electrodes are normally placed in specific scalp locations to target specific parts of the brain, stimulation extends beyond the regions beneath the electrodes and can result in unintended altering of brain functions.
Self-administered brain stimulation may have a different impact on neurons that are active during stimulation versus neurons that are inactive during stimulation, according to the neurologists. “Because of this feature, the cognitive or behavioral activity occurring while tDCS is applied will modify the effects,” said Dr. Fox. Stimulation may affect the brain differently depending on whether it is applied while the subject is watching TV, sleeping, or performing other daily tasks, he added.
In addition, while some cognitive abilities may be enhanced with tDCS, other abilities may be impacted negatively. “Such cognitive tradeoffs could develop over time and only become recognizable long after the stimulation,” said Dr. Fox. Also, small changes in tDCS settings such as current amplitude and electrode activity could result in negative effects on brain function, said the neurologists.
The authors emphasized that the response to tDCS is unpredictable; subjects respond differently to changes in cortical excitability. For example, age, gender, hormones, cognitive ability, and head anatomy can modify the effects of tDCS in the brain. “Up to 30% of experimental subjects respond with changes in cortical excitability in the opposite direction from other subjects using identical tDCS settings,” said Dr. Fox.
“We encourage consideration of these issues and involvement of health care providers in making decisions regarding DIY brain stimulation,” said Dr. Fox. He and his coauthors recommended that parents weigh the risks before using this device for children, especially since minors are not able to fully assess the potential dangers of tDCS.