College students who use marijuana regularly have lower grades — whether or not they think it affects them, according to a first-of-its-kind analysis of Minnesota student survey data.
Mean grade-point averages dropped from 3.33 to 3.01, comparing male students who didn't use marijuana at all with students who used it daily. The comparable gap for female students was 3.4 to 3.18
Researchers at Boynton Health, the student health service at the University of Minnesota, conducted the analysis after seeing a significant increase in marijuana use in initial data from a 2018 student survey.
As lawmakers in Minnesota and other states consider legalizing marijuana for recreational use, they need to see this kind of data and understand the impact of the psychoactive drug, said Dave Golden, Boynton's director of public health and communications.
"This has to be a factor in people's minds when they're taking a look at [legalization]," he said.
The analysis is based on Boynton's survey of 10,579 students at the U and 17 other schools in the state. The survey tracks trends in student behavior — including academic performance, mental health, drinking and screen time — but it typically does not cross-reference the data to see how one behavior affects another.
The share of U students who consider themselves current users — meaning they had consumed marijuana in the month before the survey — increased from 13.5 percent in 2007 to 22 percent in 2018.
Boynton's research director Katherine Lust then compared self-reported GPAs to student marijuana use and to alcohol use. While binge drinking had an association with lower grades, it was weaker than the link with marijuana.