Before being allowed to start data collection, every researcher has to gain ethical approval from their institution. This is to make sure that we don’t harm our participants by asking them potentially distressing questions or put them in danger by using unsafe techniques. When applying for ethical approval for a non-invasive brain stimulation study, for example using transcranial direct current stimulation (tDCS), one has to fill out lengthy forms giving a detailed account of all parameters such as duration of stimulation, electrode configuration, power supply etc. As is required by UK guidelines, a safety-trained person has to be present and participants have to be thoroughly screened before being allowed to take part. For example, anyone with a family history of epilepsy or suffering from a psychiatric illness, pregnant women or people who consumed alcohol within 24 hours before the study will immediately be excluded. Although guidelines are a bit overly pedantic at times, it seems sensible that nobody without proper training and a clear understanding of the method can run off with a tDCS kit, wildly stimulating people’s brains. But what if there is no institution and no ethical committee? Can a lack thereof lead to potential harm?
When searching the internet for DIY tDCS kits, already the first hit advertises a “brain-boosting kit” so called “home-enthusiasts” can buy for 99$. It promises to “speed up one’s brain” and halve learning time. On Ebay.co.uk you can even find a tDCS kit for as little as £15. The seller calls it “DIY tDCS kit”, DIY meaning that “it is your responsibility and liability to determine why and how you will use this unit”. The kit comes with 2mA to 3mA power supply but you can contact the seller if that’s not enough for you. (Note, most tDCS papers published in cognitive neuroscience use 1mA to 2mA and according to Fregni et al. (2015) standard parameters are below 2.5 mA; in comparison, a standard European toaster runs at 9A.). If the price itself is not convincing enough, a quick Google search leads you to numerous success stories of people brushing through exams in no time after having administered tDCS to themselves.
tDCS kits for home-use, however, are not only sold to boost mental ability but also as an alternative treatment for conditions such as depression, insomnia or anxiety. The Fisher Wallace Stimulator®, for example, is specifically targeted at people suffering from these conditions. The U.S. based company sells FDA-approved (U.S. Food and Drug Association) stimulator kits to patients with a doctor’s prescription (which can be bought online for 18$) in the U.S. or over the counter in Europe. Prices in the U.S. are around 699$ for a kit including “everything you need to ease your symptoms”. heir website they refer to a study published in the Journal of Nervous and Mental Disease that provides evidence for the Fisher Wallace Stimulator®’s efficany in treating depression. Interestingly, said study was supported by a research grant form Fisher Wallace Laboratories (McClure et al., 2015).
Naturally, an alternative treatment to drugs would be valuable for people suffering from mental disorders and there are indeed studies suggesting of the therapeutic effect of tDCS (for review see Meron et al., 2015). However, the question arises how efficient it is to administer tDCS in entirely uncontrolled settings and if it might cause more harm than it does good. Although tDCS is only associated with minor side effects (such as temporary itching or reddening of the skin), you are still stimulating a brain. While some sites seem to be more trustworthy than others, ordering a tDCS machine via Ebay generally doesn’t involve any screening for metal implants or a family history of epilepsy. Hence, I wonder if – quite apart from the doubtful efficiency – a home-enthusiast’s attempt to boost their mental ability has ever backfired. In July 2016, 39 experts in tDCS signed an “Open Letter Concerning Do-It-Yourself Users of Transcranial-Direct-Current Stimulation” (Wurzman, Hamilton, Pascual-Leone, & Fox, 2016). They caution not only against the acute potential harms, such as skin irritation, but also potential long-term effects. At research institutions we have ethical guidelines and safety procedures for a reason: to protect our participants. The protection of patients or participants is not always and probably rarely can be provided by companies or websites selling brain stimulation kits online. Therefore, there should be more control over selling and buying brain stimulation kits online (as for example executed by websites such as Ebay) or simply more awareness of the potential risks being raised. In an attempted to call for globalised standard parameters Fregni and colleagues (2015) published a paper in which they suggested that a stimulation duration of 60 minutes per session or more than two session per day shouldn’t be exceeded, as not doing so would result in substantial risk. There is evidence suggesting that continuous use of tDCS affects neuroplasticity, but if the stimulation parameters are chosen wrongly this might lead to maladaptive rather than positive changes (Fregni et al., 2015).
If on the other hand, this concern is unfounded, one cannot potentially make any mistakes and stimulating one’s own cortex doesn’t come with any risks, I wonder what this would say about the technique being used in cognitive neuroscience research. If effects are so minor that it can’t possibly have any negative consequences, tDCS is arguably not the best technique to use if looking to draw major conclusions about the human mind and brain. However, even if an effect is small it can still often be detected with a large sample size and, hence, shed further light on neural functioning, whereas in a single person that effect might impossible be observed, no matter how high of a power supply you choose. So, personally, I don’t think that tDCS is useless, and for sure this question will not be properly answered by abandoning tDCS research out of lacking evidence. In fact, it is insufficient data on long term use that prevents us from predicting what happens if a brain is regularly stimulated for months (for example, at home sitting in front of the TV). We can only get a better understanding of and improve our techniques by using them (in a safe and controlled environment).
At the time being, tDCS as a technique is still poorly understood and with accumulating evidence the standard parameters are likely to change within the next years. One has to have an understanding of the developing literature on this technique to keep up to date with what is considered safe user guidelines. Arguably, not every “home-enthusiast” has this understanding. As Fregni et al. (2015) point out in their paper, a global effort is needed to arrive at a conclusion to either confidently continue using or abandon tDCS (should it be shown to be ineffective), based on studies under controlled settings. Because our current data is still insufficient to know all the potential harms, we should err on the side of caution and stick to guidelines even if they seem pedantic, and I don’t think people would be well advised to order kits online and testing them on themselves, especially when there is no medical need. After all, a technique that is easy to use is most likely also easy to misuse.
Fregni, F., Nitsche, M. A., Loo, C. K., Brunoni, A. R., Marangolo, P., Leite, J., … Bikson, M. (2015). Regulatory Considerations for the Clinical and Research Use of Transcranial Direct Current Stimulation (tDCS): review and recommendations from an expert panel. Clinical Research and Regulatory Affairs, 32(1), 22–35. https://doi.org/10.3109/10601333.2015.980944
McClure, D., Greenman, S. C., Koppolu, S. S., Varvara, M., Yaseen, Z. S., & Galynker, I. I. (2015). A Pilot Study of Safety and Efficacy of Cranial Electrotherapy Stimulation in Treatment of Bipolar II Depression. The Journal of Nervous and Mental Disease, 203(11), 827–835. https://doi.org/10.1097/NMD.0000000000000378
Meron, D., Hedger, N., Garner, M., & Baldwin, D.S. (2015). Transcranial direct current stimulation (tDCS) in the treatment of depression: Systematic review and meta-analysis of efficac and tolerability. Neurosci Biobehav Rev, 57, 46-62. doi: 10.1016/j.neubiorev.2015.07.012. Epub 2015 Jul 29.
Wurzman, R., Hamilton, R., Pascual-Leone, A., & Fox, M. (2016). An open letter concerning do-it-yourself (DIY) users of transcranial direct current stimulation (tDCS). Annals of Neurology, 1–4. https://doi.org/10.1002/ana.24689