Science journals New Scientist and Nature have both recently run articles about transcranial direct-current stimulation (tDCS). The 12 April issue of the New Scientist (no. 2807) had an article entitled “Mind controls: Running electricity through the skull”, while the 13 April issue of Nature (no. 472) called their article “Neuroscience: brain buzz”. tDCS involves sending a current of one or two milliamps through the head. It was tried about 50 years ago, but has recently been in the news as researchers have been trying to establish that it can improve people’s performance on various tests, tasks or computer games, etc.
Both the New Scientist and Nature articles mentioned electroconvulsive therapy (ECT). The New Scientist had this to say:
“tDCS should not be confused with electroconvulsive therapy, where a much larger shock of 600 milliamps is applied to the whole brain. ECT is designed to trigger seizures and must be done under a general anaesthetic. It has side effects such as memory loss and confusion and so is only given to people with very serious depression.”
While Nature said:
“By the 1940s, many patients with depression were being given electric shocks to the temples that were strong enough to induce seizures — so-called electroconvulsive therapy. But for decades people toyed with the idea of treating mental illness with electric shocks that were much milder — 1,000 times less intense than electroconvulsive therapy.”
Both articles mention ECT only as a comparison to tDCS, to point out how small the amount of electricity involved is compared to ECT, which explains the unusual terms they use in relation to ECT. It is very rare to find, when people write about ECT, something as factual as a “shock of 600 milliamps”. I think 600 milliamps is still on the low side, the latest Ectron machine for example, delivers a current of 750 or 900 milliamps, while with the Thymatron System IV in the US it is 900 milliamps and with recent Mecta machines 550-800 milliamps. But at least it has the right number of noughts.
Sometimes you find people describing the current used in ECT as “small” or “very small”. This patient information leaflet, for example, talks about a “very small current”. And one textbook (Mental health care for elderly people, 1997, edited by Ian J Norman and Sally J Redfern) talks about a how “very small current (a few mAmps)” is used. 900 – a few? In considering 900 milliamps as a very small current, those who work in the field of psychiatry are out of step with the rest of medicine. In the June 2010 issue of the journal Anesthesia and Analgesia, an article on electrical safety in the operating room by Steven J Barker and D John Doyle explains the terminology:
“The severity of an electrical shock is determined by the amount of current (amperes, A) and the duration of the current flow. In medical terms, electrical shocks are usually divided into two categories. Macroshock refers to larger currents (typically more than 10 mA) flowing through a person, which can cause harm or death. Microshock refers to very small currents (as little as 10–50 μA) and applies only to the electrically susceptible patient…”
That puts ECT, with a current more than 50 times bigger than 10mA, definitely in the macroshock category.