The study, among 181 college students in California, found that those who were vaping with e-cigarettes that had the highest concentration of nicotine were much more likely to be smoking the real thing within six months.
And if they hadn't moved on to cigarettes, they were certainly more likely still to be vaping, researchers from the University of Southern California discovered.
The students were smoking e-cigarettes with a range of levels of nicotine content, from zero to 18 mg/mL or higher.
E-cigarettes that contain nicotine are now classified as tobacco products, and are regulated in the same way as cigarettes by America's Food and Drug Administration (FDA).
But what do we really know about the long-term safety of vaping? Apparently, not a lot, and so a group of UK politicians is setting up a special enquiry to investigate "the significant gaps" in our understanding.
It will also explore vaping's effectiveness as a stop-smoking tool, and if they are having less of an impact on poor health than real cigarettes.
The announcement follows a decision to include e-cigarettes in a UK government 'stop smoking' campaign that recommends them as a way to wean smokers off cigarettes.