Doctors have been warned to think twice before recommending smokers switch to e-cigarettes. Scientists say more research is needed on the gadgets - and say they could also be harming people's health.

This study is believed to be the first to measure attitudes toward e-cigarettes among physicians treating adult smokers.

'Even in the absence of evidence regarding the health impact of e-cigarettes and other vaping devices, a third of physicians we surveyed are recommending e-cigarettes to their patients to help quit smoking,' said Leah Ranney, PhD, one of the authors of the survey and associate director of the Tobacco Prevention and Evaluation Program at UNC.

'Yet, e-cigarettes are not approved by the FDA for smoking cessation. It is clear that physicians should refrain from recommending e-cigarettes until more is known about their safety,' Leah Ranney said.

The study found that physicians were more likely to recommend e-cigarettes when their patients asked about them or when the physician believed e-cigarettes were safer than smoking standard cigarettes.  However, physicians often have inconsistent information about the safety of using e-cigarettes and in this survey 13 percent are unaware that e-cigarettes are not approved by the FDA.

'Physicians may choose to use FDA approved medications rather than devices and products not approved by FDA,' says Dr. Adam Goldstein, a UNC Family Medicine physician and study co-author.

The researchers concluded that the area needed more research.