Not sure why people are downvoting w/o commenting. It seems like the study concluded what you are saying - that vaping / eCigs do increase the likelihood you will start smoking actual cigarettes.
Right, which was that parents point - that it cuts both ways. There are people who get off cigarettes by moving to vaping, which is great! But you don't often hear people talking about the opposite, that vaping can also lead people to smoking cigarettes.
How about: Nicotine users more likely to use nicotine.