Marijuana use among Oregon college students has gone up since the legalization of recreational pot, a new study found.

Much of that increase was among students who had recently been binge drinking.

The study, published by researchers at Oregon State University in Corvallis, is the first of its kind. Though recreational marijuana became legal in Oregon in July 2015, no research has been done on the effect on adults in general and college students in particular, said David Kerr, lead author and associate psychology professor at OSU.

The study indicates that legalization has led to an increase in the percentage of college students who use marijuana, Kerr said.

The researchers expected that. Pot is now sold in stores instead of on the street corner, it's more socially accepted and criminal penalties have fallen away.

Eight states -- Oregon, Washington, California, Alaska, Maine, Massachusetts, Nevada and Colorado -- have legalized recreational marijuana. Twenty-nine allow medical use.

Nationwide, marijuana use on college campuses is up. A large study published by the University of Michigan in April showed that more students used pot for the first time in 2015 than in the previous three decades, with about one in five students partaking.

That's comparable to Oregon's rate in 2013. But in 2016, after legalization, nearly 26 percent of Oregon college students reported using marijuana, researchers found.

The study is based on self-reported answers to a nationwide college survey that includes questions on marijuana and other substance use. The researchers used data from one public university in Oregon and compared that with six other private and public universities or colleges in states that have not legalized recreational marijuana. They used the latter as a control group.

To use the data, the researchers agreed not to publish the names of the colleges and universities.

The researchers looked at marijuana use at each institution in 2016. In Oregon, they compared that with responses to the 2013 survey. For the other institutions, they used responses between 2012 and 2015, depending on what was available. They were unable to use the same pre-legalization year for all of the colleges and universities because the data were inconsistent.

Though the researchers expected to see a bump in use after legalization, they found it was not just for those 21 and older, who are allowed to buy in stores. In fact, the highest rates were for students younger than 21.

Binge drinkers had by far the highest usage. Binge drinking students in Oregon were 73 percent more likely to report marijuana use compared with their peers in other universities.

Kerr said the results do not reflect the result of alcohol but rather say something about the type of person who drinks heavily.

"Those who binge drink may be more open to marijuana use if it is easy to access, whereas those who avoid alcohol for cultural or lifestyle reasons might avoid marijuana regardless of its status," Kerr said.

Binge drinking is common among college students. About 55 percent reported drinking four to five drinks within two hours in the previous two weeks.

The study did not find an increase in binge drinkers, and rates of those who used tobacco actually fell.

The study, published in the journal Addiction, is just a start. Kerr said more work needs to be done to analyze the effects of marijuana legalization.

"Americans are conducting a big experiment with marijuana," Kerr said. "We need science to tell us what the results of it are."

-- Lynne Terry