E-cigarettes are often marketed as a bridge to quitting smoking, but recent data suggest the increasingly popular devices may not actually help smokers kick the habit. A new U.S. study casts doubt on the utility of electronic cigarettes as a quit-smoking tool.

The report, published in the Journal of the American Medical Association, found that smokers who used e-cigarettes in addition to normal cigarettes were no more likely to quit than those who didn’t use e-cigs. Researchers studied tobacco use among 949 smokers, 88 of whom also used e-cigarettes. Their data were based on self-reported responses over the course of one year.  

"We did not find a relationship between using an e-cigarette and reducing cigarette consumption," Rachel Grana, lead author of the study, told Reuters.

The debate over whether e-cigarettes can help people quit smoking is murky, given that the science on the issue is still relatively sparse. Even the authors of the latest study admit their research consisted of a small sample size and they caution against using their data to draw any definitive conclusions. As the Washington Post notes, researchers failed to collect qualitative information about the smokers’ habits, such as frequency or motivation.

"Nonetheless, our data add to current evidence that e-cigarettes may not increase rates of smoking cessation,” the authors wrote. "Regulations should prohibit advertising claiming or suggesting that e-cigarettes are effective smoking cessation devices until claims are supported by scientific evidence."

E-cigarettes first came on the market in China in 2004. Over the past decade, e-cigs have grown into a $2 billion industry. The battery-powered devices contain a liquid form of nicotine that is extracted from tobacco and infused with flavorings and colorings.

Much of the controversy surrounding e-cigs is over how strictly they should be regulated. Currently, the federal government does not regulate e-cigarettes. The Food and Drug Administration has said it plans to set new standards for e-cigarettes, much like nicotine gums and patches, but has yet to lay out a plan.