MORE evidence is in that so-called e-cigarettes do let smokers stop smoking. Such cigarettes deliver to the user an oral nicotine hit without the associated carcinogens and other noxious chemicals found in tobacco smoke, by evaporating a solution containing the drug. A study just published in Addiction by Jamie Brown of University College, London, and his colleagues suggests they are 60% more successful at getting people to give up tobacco by themselves (ie, without enrolling on a formal anti-smoking programme) than either willpower alone or previously available quitting aids like nicotine patches.

Dr Brown and his team looked at data collected by the Smoking Toolkit Study, a surveillance programme run by them, and paid for by Cancer Research UK, a charity, and Britain’s health ministry. This programme tracks smokers’ behaviour in England, month by month, and has been asking about e-cigarettes since July 2009. The questions posed to participants include whether they have tried to give up smoking, have succeeded, and what approach they have taken.

Among those who had gone it alone, rather than opting for a doctor’s assistance to help them quit, the researchers found (on the basis of the raw data) that people who had employed e-cigarettes for the purpose in the previous 12 months were more than twice as successful as those who had used other devices, such as nicotine patches. A big win, apparently, for e-cigarettes—though, intriguingly, they were only 40% more successful than relying on willpower by itself.

As that second number indicates, in a study like this the raw figures can mislead. So Dr Brown put his numbers through the statistical wringer by controlling for other variables such as just how addicted to nicotine a respondent was. That done, e-cigarettes had an almost identical advantage (a bit more than 60%) over the other two approaches—suggesting not only that e-cigarettes were the clear winner, but also casting doubt on the value of things like patches over sheer, unadulterated willpower. (To be fair, patches are a successful way of quitting when used under medical supervision rather than just bought over the counter.) Dr Brown’s “real world” survey thus backs up formal clinical trials of e-cigarettes, which also show their virtues as quitting aids.

Why they are so successful is not yet proven. But a reasonable guess hangs on the meaning of the word “quitting”. Probably, though the Smoking Toolkit Study’s data do not address this question, most of those who take up e-cigarettes see them as a way of continuing to consume nicotine. They are, in other words, quitting tobacco, not their drug of choice. Those who use patches or willpower, by contrast, wish to quit the addiction.

The former is surely easier than the latter. From a health point of view, though, the motive hardly matters. Though e-cigarettes are too recent an invention to be sure they carry no health risks at all, those risks are clearly negligible compared with the ones that come with breathing in, several dozen times a day, the smoke from dried, burning plant leaves.