During a single month, researchers identified over 7m tweets referring to marijuana, with “pro-pot” messages outnumbering those opposed to the drug by 15 to one.
Most of those sending and receiving “pot tweets” were under the age of 25, and many in their teens, said the team.
US psychiatrist and lead author Dr Patricia Cavazos-Rehg, from the Washington University Institute for Public Health, said: “It’s a concern because frequent marijuana use can affect brain structures and interfere with cognitive function, emotional development and academic performance.
“The younger people are when they begin using marijuana, the more likely they are to become dependent.”
The findings, reported in the Journal of Adolescent Health, follow a computer search of tweets conducted between February 5 and March 5 last year.
Working with social media analytics company Simply Measured, the researchers looked for every tweet that mentioned marijuana.
Using search terms such as “joint”, “blunt”, “weed”, “stoner” and “bong”, the team turned up more than 7.6m tweets referencing the drug. An examination of a random sample of almost 7,000 tweets from these accounts revealed that 77% were pro-marijuana, 5% against, and 18% neutral.
People tweeting pro-marijuana messages had more than 50m Twitter followers — around 12 times more than those tweeting anti-marijuana messages.