A large study in England has found that smokers trying to quit were substantially more likely to succeed if they used electronic cigarettes than over-the-counter therapies such as nicotine patches or gum. These results offered encouraging but not definitive evidence in the contentious debate about the risks and benefits of these increasingly popular smoking devices.

Researchers interviewed almost 6,000 smokers who had tried to quit on their own without counseling from a health professional. About a fifth of those who said they were using e-cigarettes had stopped smoking at the time of the survey, compared with about a tenth of people who had used patches and gum.

“This will not settle the e-cigarette issue by any means,” said Thomas J. Glynn, a researcher at the American Cancer Society, who was not part of the study, “but it is further evidence that, in a real-world context, e-cigarettes can be a useful, although not revolutionary, tool in helping some smokers to stop.”

The use of e-cigarettes has risen rapidly across Europe and the United States, and regulators are scrambling to figure out how to respond in the absence of hard evidence about their effects. The debate is particularly fierce in the United States, where some experts say the devices could lure children to start smoking, while others contend that they are the best hope in generations to get smokers to switch to something less dangerous than traditional cigarettes.