The rate of marijuana use by young people of college age is at its highest point in more than 30 years, according to research from the University of Michigan. The findings are from the ongoing Monitoring the Future study of drug use by young people and adults. The research is funded by the National Institute on Drug Abuse at the National Institutes of Health.

The study found that marijuana use by young adults age 19-22 rose in 2017, continuing a decade-long trend. John Schulenberg, a researcher and one of the study’s authors, attributed the rise to evolving perceptions of cannabis use.

“In this country, laws are changing, attitudes are changing, people are not perceiving use, even regular use, as dangerous as they used to,” said Schulenberg.

The research found that 38 percent of full-time college students aged 19-22 reported using marijuana at least once in the past 12 months and that 21 percent had used cannabis in the last 30 days. The figures, which equal those from the 2016 study, are the highest since 1987. Twenty-seven percent of those surveyed believe cannabis use poses a great risk of harm, the lowest level since 1980. The Monitoring the Future study has been conducted each year since 1975.

Schulenberg said that the regular use of cannabis, which is also on the rise, can have negative consequences, especially for the heaviest users.

“And this could be the problem,” Schulenberg said. “On this daily use, the scientific evidence is pretty clear that this gets in the way of things, and it can be associated with, if not contributing to, a decline in mental health. If one is involved in heavy use, and they continue with that, then their health and wellness and happiness is probably not as high as those who do not use or do not continue to use.”

Sheila Vakharia, a policy manager at the Drug Policy Alliance, said that cannabis use doesn’t necessarily equate with misuse or abuse.

“There’s a difference between trying and experimenting, and actually having a problem,” Vakharia said. “We don’t know if these people are smoking weed and then missing class, slacking on assignments, and if starting on marijuana has impacted relationships with family and friends.”

Use Among Young Adults Not In College Even Higher

The study found that the rate of marijuana use by non-college students age 19-22 was even higher. In that group, 41 percent said they had used cannabis in the last year and 28 percent reported using marijuana in the past 30 days. Regular users, those who had used at least 20 of the previous 30 days, totaled 13.2 percent. For college students that number was only 4.4 percent.

Schulenberg said that heavy marijuana use by young people may have significant risks.

“The continued increase of daily marijuana use among noncollege youth is especially worrisome,” said Schulenberg. “The brain is still growing in the early 20s, and the scientific evidence indicates that heavy marijuana use can be detrimental to cognitive functioning and mental health.”

Schulenberg said that the researchers were planning further study to try to determine the cause of the difference in cannabis use rates among college students and their peers not going to school.

“We’ve got a zillion ideas,” he said. “We just don’t know what the science is.”