A new study has found that people who use electronic cigarettes do not report higher rates of quitting than regular cigarette smokers.
The findings were based on survey answers from 949 smokers, reported in a research letter to the Journal of the American Medical Association (JAMA) Internal Medicine.
Just over 13 percent of the people in the study reported quitting smoking within one year.
E-cigarette use "did not significantly predict quitting one year later," said the letter, written by three researchers at the University of California, San Francisco.
Among participants who reported using both e-cigarettes and regular cigarettes, e-cigarette use was not associated with a change in cigarette consumption, it added.
The fact that there were so few e-cigarette users in the study -- just 88, and nine of whom quit -- may have made any trends more difficult to spot, said the letter.
"Nonetheless, our data add to current evidence that e-cigarettes may not increase rates of smoking cessation," it said.
"Regulations should prohibit advertising claiming or suggesting that e-cigarettes are effective smoking cessation devices until claims are supported by scientific evidence."
E-cigarettes deliver nicotine through a vapor, and are currently not regulated by health authorities in the United States.