E-cigarettes were nearly twice as effective as nicotine patches, gums and similar therapies in helping people stop smoking cigarettes, a study published Wednesday in the New England Journal of Medicine found.

Researchers at the Queen Mary University of London conducted a randomized clinical trial on 886 participants who were attending the U.K. National Health Service's stop-smoking services. People were divided into two groups and were told they could use either an e-cigarette or nicotine-replacement products of their choice, with options including nicotine patches and gums. Both groups received weekly one-on-one sessions with local clinicians.

One year later, researchers invited people who said they stopped smoking to come in for a carbon monoxide test to confirm their answer. They found 18 percent of people in the e-cigarette group had stopped, compared with 9.9 percent in the nicotine-replacement group.

Doctors have been wary of recommending people use e-cigarettes as a way to wean themselves off conventional cigarettes, citing both the lack of evidence showing they work and lack of data on the long-term health effects of using the products. The new study may quell some of those concerns. However, the study is also likely to receive some pushback because it was conducted in the United Kingdom, which has embraced and even encouraged e-cigarettes as an alternative for adult smokers.

In an editorial accompanying the study, professors from the Boston University School of Medicine urged doctors to use caution when recommending e-cigarettes for smoking cessation. They said doctors should only recommend e-cigarettes when an FDA-approved treatment fails, and that if doctors do suggest e-cigarettes, they should manage their use like they would with other products.

"While e-cigarettes are 'safer' than traditional cigarettes, they are not without risks," Boston University professors Belinda Borrelli and George O'Connor said in a statement.

They also pointed to the finding that at the one-year mark, 80 percent of people in the e-cigarette group were still using the devices. So while people stopped smoking cigarettes, they were still using e-cigarettes. The study's authors also noted this finding, saying it "can be seen as problematic if e-cigarette use for a year signals ongoing long-term use, which may pose as-yet unknown health risks."

Huge numbers of teens using the products — particularly one brand, Juul — have soured perceptions about e-cigarettes in the U.S. Even Food and Drug Administration Commissioner Scott Gottlieb, who has championed the devices as a way to help adult smokers, says the industry is at a tipping point.

Ray Niaura, a professor of social and behavioral sciences at New York University, said the study's results are "encouraging." They also suggest researchers can find ways to keep more people cigarette-free longer, said Niaura, who was not involved in the study.

At the six-month mark, 35 percent of people in the e-cigarette group were still cigarette-free. That dropped to 18 percent at the one-year mark.