New research shows that e-cigarettes may not help smokers kick the habit, but the methodology has some health experts questioning whether the findings actually reveal anything about the device’s safety or capacity to reduce tobacco-related illness.

Dr. Pamela Ling, a tobacco researcher at the University of California, San Francisco, and co-author of the new study, said that the investigation found no evidence supporting the widespread claim that e-cigarettes aid cessation among users. “We found that there was no difference in the rate of quitting between smokers who used an e-cigarette and those who did not,” she said, speaking to Nature.

“Advertising suggesting that e-cigarettes are effective for smoking cessation should be prohibited until such claims are supported by scientific evidence,” she added.

The study, which is published in the journal JAMA Internal Medicine, followed 949 men and women who were asked to detail their smoking habits in an online survey. Eighty-eight participants said they had used or were using e-cigarettes. The researchers then compared the sample’s rate of cessation with that of the e-cigarette subset.

Case Closed?

With no significant difference observed between the two groups, it would appear that e-cigarettes have little effect on a smoker’s habits. But as several experts have pointed out, the methodology of the study does not permit any conclusions about the device’s capacity to aid quitting. The study simply determines how likely e-cigarette users are to quit.

If this methodological difference seems a bit fuzzy, try replacing the subset “e-cigarette user” with “smokers with ready access to quitting aids.” In order to evaluate the efficacy of this particular attribute, you’d have to look at success rates among the smokers who are actually trying to quit — not simply the likelihood of any subject quitting.

According to Peter Hajek, director of the Tobacco Dependence Research Unit at the Barts and the London School of Medicine and Dentistry, said that the conclusion drawn by the authors are “just not related in any way to the study finding.” He added that many researchers currently think e-cigarettes represent “the best hope so far to put a stop to smoking-related death and disease by replacing deadly cigarettes with a safer alternative.”

Similarly, in an Italian study published in 2013, researchers from the University of Catania found that heavy smokers who switched to a daily pack of e-cigarette nicotine cartridges quickly reduced their tobacco intake, with some dropping the habit entirely within three months. Although the study was not originally intended as a cessation test, 13 percent of the heaviest smokers had quit cigarettes by the end of the trial.

Source: Grana RA, Popova L, Ling PM. A Longitudinal Analysis of Electronic Cigarette Use and Smoking Cessation. JAMA Internal Medicine. 2014.