Nowadays, your Twitter feed is likely consumed with an endless barrage of politic rants, sports highlights, and cat GIFS. But beneath all the headlines and commentary is useful data that is becoming more and more important to public health research.

Case in point: The growing e-cigarette trend.

To better understand why people start using e-cigarettes in the first place, as well as why they continue vaping, San Diego State University researcher and public health expert John W. Ayers mined and analyzed Twitter data from over 3 million public tweets in 2012 and in 2015. (With Twitter data in particular, Ayers argues, researchers can "listen in to what people are naturally saying about e-cigarettes to their friends rather than a surveyor.")

His finding: People's reasons for vaping have changed noticeably and somewhat surprisingly, according to the work published Thursday in the journal Plos One.

In 2012, 43% of tweets indicated that people started vaping because they wanted to quit "combustibles" (a.k.a. cigarettes and other "analog" smoking tobacco products), the research indicated. In second place came "social image" (21%), followed by the convenience of vaping indoors (14%), available flavors (14%), percieved safety (9%), lower cost (3%), and better smell (2%).

In 2015, however, our tweeting vapers seemed to change their minds. While mentions of "quitting combustibles" significantly declined, tweets pertaining to "social image" dramatically rose to 37%, making it the most common reason people said they'd started vaping.

To summarize: "The reasons people vape shifted away from cessation and toward social image during the time that e-cigarettes evolved from a cessation device to a freestanding tobacco product attracting smokers and nonsmokers alike," said Jon-Patrick Allem, one of the study's co-authors and a fellow at the University of Southern California's Tobacco Center of Regulatory Science.

But if there's one thing to take away from this study, it's that some of the reasons users cited—like lower cost and cessation—can in fact be misleading. For example, "vaping may be no less expensive than smoking combustibles," said Eric Leas, another co-author and graduate student at UCSD. And if quitting "combustible" cigarettes is your ultimate goal, it's important to know that one study found that using e-cigarettes may actually decrease your chances of quitting.