E-cigarettes, facing municipal bans and scrutiny by U.S. regulators, got a new slap on the wrist from scientists: A report last week suggests the devices may be a gateway to old-fashioned, cancer-causing smokes for teens.

Youths who reported ever using an e-cigarette had six times the likelihood of smoking a traditional cigarette than those who never tried the device, concluded a study in JAMA Pediatrics. E-cigarette use didn't stop young smokers from partaking in regular cigarettes as well.

The world market for e-cigarettes may top $5 billion this year. Makers of the devices, including Altria Group Inc., the largest U.S. tobacco firm, market them online and on TV, where traditional tobacco ads are banned, and some have added flavors such as bubble gum to the nicotine vapor that may have extra appeal for youths. That allure is why the U.S. Food and Drug Administration should restrict the devices, anti-smoking advocates say.

Concerns about underage use of e-cigarettes were raised last year when the U.S. Centers for Disease Control and Prevention reported that use of the devices by youths doubled in 2012 from a year earlier.

- Bloomberg News