High-profile Twitter users who tweet about hookah are often writing about how people should smoke it, according to a new study out of Washington University. Officials at the Centers for Disease Control and Prevention caution that this promotion of hookah is a dangerous trend, since smoking it comes with many of the same health risks as smoking cigarettes.

The study — published in the CDC's Preventing Chronic Disease journal — analyzed references of the word "hookah" from the 14.5 billion tweets posted between April and May 2014. Researchers reviewed a randomized 5,000-tweet sample of these messages, specifically those from high-profile Twitter users. ("High-profile Twitter users" were, for the purposes of this study, those in the top 25 percent of the sample, as ranked by Klout score and number of followers.)

Nearly all of the tweets about hookah were promotional, either encouraging others to smoke it or talking about it favorably; only 7 percent talked about hookah in a negative way. In about half of the positive tweets, the person writing them either wanted to smoke hookah or was currently smoking it. Other drugs were also often referenced along with hookah in the tweets.

The study authors argue that these tweets are potentially harmful for younger twitter users, who may feel encouraged to take up hookah.

"Peer attitudes and habits are one of the most important influences on youth substance use behaviors," says study author Melissa Krausse, a professor in the department of psychiatry at Washington University in St. Louis. "Exposure to social media messages that present hookah in a positive light or as a normal behavior could influence the attitudes and behaviors of youth and young adults who view these messages."

Hookah — also known as shisha — is a single- or multi-stemmed water pipe used for vaporizing and smoking flavored tobacco. Hookah use more than doubled among middle school and high school students between 2013 and 2014. The practice has been linked with many of the same health effects that are caused by smoking, including lung cancer and respiratory disease, as well as decreased fertility. Hookah has also been found to contain toxic agents like carbon monoxide and cancer-causing metals.