Washington, Jan 23 (IANS): Pro-marijuana "tweets" are multiplying on the micro-blogging site, finds a study, adding that most of those sending and receiving "pot tweets" were aged under 25.

After analysing every marijuana-related Twitter message sent during a one-month period in early 2014, researchers at Washington University's school of medicine in St Louis found that the "Twitterverse" is a pot-friendly place.

In that period, more than seven million tweets referenced marijuana with 15 times as many pro-pot tweets sent as anti-pot tweets.

"Although we cannot yet link pro-pot tweets to actual drug use, we should be worried because many people are receiving these messages are at an age when they are most likely to experiment with drugs and develop problems with substance use," explained Patricia A Cavazos-Rehg, assistant professor of psychiatry.

It is a concern because frequent marijuana use can affect brain structures and interfere with cognitive function, emotional development and academic performance, Cavazos-Rehg added.

In the new study, Cavazos-Rehg and her colleagues worked with social media analytics company Simply Measured to find every tweet about marijuana sent from Feb 5 to March 5, 2014.

They conducted computer searches using search terms such as "joint," "blunt," "weed," "stoner" and "bong" to discover more than 7.6 million tweets related to pot.

The researchers found that 77 percent were pro marijuana, five percent were against pot and 18 percent were neutral.

People tweeting pro-marijuana messages had a total of more than 50 million Twitter followers, about 12 times more than those tweeting anti-marijuana messages.

"Many people believe marijuana use is harmless and social media conversations almost certainly drive some of those opinions, making the drug appear socially acceptable," the authors pointed out.

The findings were reported online in the Journal of Adolescent Health.