A new study published in the American Journal of Preventive Medicine purports to show that the use of e-cigarettes causes long-term lung damage. [...] This is critical because it shows that in order to control for smoking history properly in a study such as this one, you cannot merely control for whether or not someone was a current or ever smoker at baseline. You have to actually control for the person's overall smoking history including whether they were a heavy smoker and how many years they smoked.