Washington, Sep 12 (IANS): Percentage of US college students using marijuana was at the highest level in 2016 since the past three decades, according to a study conducted by University of Michigan researchers.

The national Monitoring the Future follow-up study, funded by the the National Institute on Drug Abuse, showed in 2016, 39 per cent of full-time college students aged 19-22 indicated that they used marijuana at least once in 12 months, and 22 per cent indicated that they used at least once in 30 days, reports Xinhua news agency.

Both of these 2016 percentages were the highest since 1987, and represented a steady increase since 2006, when they were 30 and 17 per cent, respectively.

Daily or near daily use of marijuana-defined as having used 20 or more times in the prior 30 days-was at 4.9 per cent in 2016; this is among the highest levels seen in more than 30 years, though it has not shown any further rise in the past two years.

"These continuing increases in marijuana use, particularly heavy use, among the nation's college students deserve attention from college personnel as well as students and their parents," John Schulenberg, the current principal investigator of the Monitoring the Future follow-up study, said on Monday. 

"We know from our research and that of others that heavy marijuana use is associated with poor academic performance and non-completion of college.

In 2016, 30 per cent of those aged 19-22 perceived regular use of marijuana as carrying great risk of harm, the lowest level reached since 1980.

These findings come from the long term Monitoring the Future study, which has been tracking substance use of all kinds among American college students for the past 37 years.