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It’s official: Twitter loves #weed

Johnny Caceres stacks bundles of the new SF Evergreen, the San Francisco Bay Area's first marijuana-themed monthly newspaper, on January 22, 2015 in San Francisco, California. (Justin Sullivan/Getty Images)

We've suspected this for awhile, but now we finally have the science to prove it: Twitter users are overwhelmingly pro-marijuana.

Researchers from the Washington University School of Medicine have found, first, that roughly 1 out of every 2,000 tweets is about marijuana. That adds up to about 7.7 million weed-related tweets per month, according to their analysis of the totality of tweets in February of 2014. The table below (which includes, perhaps, the best collection of footnotes ever to grace the pages of an academic journal) contains the keywords they used to determine whether a tweet was weed-related or not.

To measure the sentiment behind these tweets, they randomly sampled 7,000 of them from Twitter users who had both a high number of followers (greater than 755) and a high Klout score (greater than 44). Among these influential tweets, 77 percent were pro-weed, 18 percent were neutral, and only 5 percent were anti-marijuana. That would suggest that pro-weed sentiment is 15 times more common on Twitter than anti-weed sentiment.

The researchers then categorized the pro- and anti-weed tweets into certain common themes among them. Among the pro-weed crowd, simply stating that you want weed or plan to smoke some was the most common type of tweet. Talking about heavy use, legalization, and weed and relationships was also popular.

Anti-weed tweeters, on the other hand, tended to characterize pot smokers as unproductive losers. They also said that smoking weed is unattractive and/or gross. Some were from current smokers talking about the harm of the drug, or saying that they want to quit.

The researchers note, with some alarm, that most of the people tweeting about weed were relatively young. "The concern that we have about pro-marijuana Twitter chatter is the potential for social contagion and increased marijuana use in adolescents," they write. This has been the theme of most of the press coverage of the study.

On the other hand, young adults -- the 18 to 26 crowd -- have long been the most active users of marijuana. So it's not any surprise that Twitter, which skews overwhelmingly young, would be a hotbed of pro-pot sentiment. More broadly, Twitter users are a small and demographically unique slice of the total U.S. population, so it's difficult to make generalization about the broader public based on a sample of tweets, no matter how comprehensive.

The authors acknowledge that they "cannot verify the degree to which tweets correspond with marijuana use." And indeed, the latest national data  -- collected over the same period as the tweets in this report -- finds teen marijuana use edging downward. In other words, it seems likely that social media chatter is a reflection of adolescent behavior regarding marijuana use -- not a driver of it.