Self-improvement types who aren't afraid to be their own guinea pigs are rigging up their brains to electric currents to chase neuroenhancement—attempting to boost their working memory, for example. But scientists still barely understand how transcranial direct current stimulation (tDCS) works, or what sort of long-term effects it might have.
In an open letter published on July 7 in the Annals of Neurology, a team of experts warns against DIY brain stimulation, listing off a few potentially very worrisome side-effects. Maybe most concerning, the paper says, the enhancement of certain cognitive abilities might come at the cost of others, and whatever damage is done could be long-term, maybe permanent.
tDCS is cheap and fairly easy to do, which is part of its appeal to researchers and DIYers. It involves strapping electrodes to targeted spots on the scalp, and passing a weak current between them.
"There are a lot of [parts] you can just buy at Home Depot that can be repurposed, and are being, to apply self-administered tDCS at home," co-author Rachel Wurzman of the Laboratory for Cognition and Neural Stimulation at the University of Pennsylvania told me.
On reddit forums, people who've tried it (or want to) trade tips and tricks about tDCS, like "if you put this electrode here, you get this effect," she continued. It's popular with gamers, but also with people suffering from anxiety or depression, who think it could help.
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Motherboard's own Jason Koebler gave it a shot. "I only tried it a couple times," he said. "During the sessions, my head was tingling but it wasn't painful. Kind of a pleasant buzzing sensation that eventually turned a little bit uncomfortable toward the end of the session."
"I would say the effects felt like a mild cup of coffee in that I definitely felt something had happened but it was a weak effect either way. I never did any tests to determine if my brain function temporarily improved," he told me via Slack chat.
Researchers are investigating tDCS for all kinds of reasons—to see whether it could ease depression or anxiety, or help stroke patients. There's also compelling evidence that it can enhance certain cognitive abilities, at least in the short term, "but it's not approved for the treatment of any condition," said Wurzman, who researches brain plasticity after neuroinjury.
Wurzman told me that tDCS isn't even well-understood by researchers. And it can be unpredictable. In the lab, "we're seeing an effect, and it's a very valid effect," she said, "but that doesn't necessarily say anything about how an individual is going to respond."
The paper notes that certain side effects, like the possibility of skin burns, are well described by this point. Others are mysterious, but concerning. It warns that people seem to respond differently to brain stimulation depending on what they're doing: "Stimulation while reading a book, meditating, visually fixating on a point, watching TV, doing arithmetic, sleeping or playing video games could all cause different changes in the brain," it says.
Even the time of day it's administered can apparently change its effects, although the reasons why aren't clear.
"We have seen very variable responses, from individual to individual," Wurzman said. "Maybe one-third of research subjects will have an [inhibitory] response" to a certain type of stimulation, one-third will respond in the opposite way, and the other third will have a weak response, or none.
All this makes it difficult to design studies in the lab, she acknowledged. "It's like we're shooting in the dark when we're investigating these things."
The paper notes that while some cognitive abilities could be boosted with tDCS, others could be dampened. "Brain networks interact with each other, such that modifying activity in one network can change the activity in other networks," it says. Stimulating one part of the brain might "hurt the ability to perform" in another, the paper continues.
"For example, tDCS can enhance the rate of learning new material, but at the cost of processing learned material, and vice versa, depending on the stimulation site," it notes.
And changes could be long-lasting. It's hard to say exactly how long we're talking about, but the effects don't disappear overnight. "We have never formally studied tDCS at the frequency many DIY users experiment with," the paper explains, like "stimulating daily for months or longer." Studies in the lab have suggested that changes can persist at least half a year.
Zapping your brain could produce effects that are "long-lasting—for better or worse," the paper concludes. While it's exciting to think that a cognitive boost could last for months or even permanently, nothing comes for free.
Experts seem to feel that DIYers should be aware of these risks, before they hook up their precious grey matter to electrodes.