Is Noninvasive Brain Stimulation / Transcranial Stimulation Safe?


 As I mentioned in previous articles, non-invasive brain stimulation involves applying a weak electrical impulse or current to the scalp, thereby enhancing or diminishing excitability of the cerebral cortex underneath the area of stimulation. There is a growing body of scientific evidence that supports its effectiveness for use in certain neurological and psychiatric conditions. There is also evidence that it can ‘enhance cognition’ in healthy individuals.

Is it safe?

The short answer is yes. The many articles published on transcranial stimulation (over 1,000 articles within the past 15 years) record no serious adverse effects. The only common side effects encountered included pain, skin redness, or tingling at the site of stimulation. Here is what we currently know about the safety of tDCS and TMS:

tDCS Safety

  • No formal safety guidelines.
  • The most common side effects reported are mild to moderate pain, skin redness or tingling near the site of stimulation.
  • Rare reports of mania or hypomania reported in patients with depression.
  • A single seizure reported when tdcs was performed on a pediatric patient, although it is unclear whether the tDCS actually caused the seizure (as the patient had previously been diagnosed with a seizure disorder). Thus tDCS is still considered safe (Matsumoto and Ugawa, 2016).
  • Should not be used in persons with bioelectric devices such as cochlear implants, pacemakers, surgically implanted vagal nerve stimulators, deep-brain stimulators, or responsive neurostimulation devices.
  • As there is little data on its use in the pediatric population, references have recommended against its use on children.

TMS Safety

  • Requires in-clinic visits and administration by a licensed physician for all sessions.
  • The most common side effect is mild to moderate pain near the site of stimulation, which typically subsides after the first week of stimulation.
  • FDA approved for treatment of depression. There is supportive evidence that it may be effective in other neurological and psychiatric disorders.
  • Can generate seizures in 0.1% of the population.
  • Should not to be used in persons with non-removable conducting metals near or within their heads or mouths.
  • Should not be used in persons with bioelectric devices such as cochlear implants, pacemakers, surgically implanted vagal nerve stimulators, deep-brain stimulators, or responsive neurostimulation devices.
  • Avoids the systemic side effects that may be seen in psychiatric medications.
  • Does not affect cognition if used in the appropriate manner by a licensed physician.
  • Patients should be monitored closely for signs of unusual behavior/suicidal behavior, although there have been no reports of this as a side effect during clinical trials.

Are there any Long-Term Side Effects?

Long Term Side Effects are unknown at this time.

Regarding both modalities, the long-term implications of use is currently unknown. Recent statements have been released by the International Federation of Clinical Neurophysiology (IFCN) and the Annals of Neurology expressing that there are scientific risks associated with the use of tES that are time and stimulation dose dependent (IFCN, 2015; Monte-Silva et al, 2013). In other words, too long of desired stimulation can lead to the opposite desired effects (IFCN, 2015; Monte-Silva et al, 2013).

Moreover, unplanned results may occur from the ‘build-up effects of multiple sessions or from influence on non-target areas’ (IFCN, 2015). In other words, placing electrodes in the wrong positions may lead to undesired/adverse structural changes over time.




ICFN Statement on Do-It-Yourself TDCS (December, 2015)

Matsumoto, H. Yokishikazu, U. Adverse events of tDCS and tACS: A review. Clinical Neurophysiology Practice p 19-25. (2017) 

Monte-Silva, K., Kuo, M. F., Hessenthaler, S., Fresnoza, S., Liebetanz, D., Paulus, W., & Nitsche, M. A. (2013). Induction of late LTP-like plasticity in the human motor cortex by repeated non-invasive brain stimulation. Brain Stimul, 6(3), 424-432. doi:10.1016/j.brs.2012.04.01

Rossi, S., Hallett, M., Rossini, P. M., Pascual-Leone, A., & Safety of, T. M. S. C. G. (2009). Safety, ethical considerations, and application guidelines for the use of transcranial magnetic stimulation in clinical practice and research. Clin Neurophysiol, 120(12), 2008-2039. doi:10.1016/j.clinph.2009.08.01

Wexler A (2015). The practices of do-it-yourself brain stimulation: implications for ethical considerations and regulatory proposals. Journal of Medical Ethics 42, 211–215.

Wurzman, R., Hamilton, R. H., Pascual-Leone, A., & Fox, M. D. (2016). An open letter concerning do-it-yourself users of transcranial direct current stimulation. Ann Neurol, 80(1), 1-4. doi:10.1002/ana.2468