Figure 1.

Smoking habits among e-cigarette users. The bars represent all those who had ever tried e-cigarettes and all current e-cigarette users at age 19 years, respectively. Never smoker, never smoker at age 14–15 and 19 years; ever occasional smoker, occasional smoker at age 14–15 or 19 years but not a daily smoker; former smoker, either self-reported former smoker at age 19 years or being a non-smoker or occasional smoker at 14–15 years and non-smoker at 19 years; ever daily smoker, daily smoker at 14–15 or 19 years. E-cigarettes, electronic cigarettes.