Oct 08, 2015 04:54 PM EDT By Staff Reporter, UniversityHerald Reporter

New research suggests that undergraduate college students are more likely to have sex on days they used marijuana or binged on alcohol than on days they didn't.

Researchers from Oregon State University said their findings draw attention to some common but risky sexual behaviors in college students, especially since binge drinking and being in a serious dating relationship also were linked with less condom use, putting young adults at risk for sexually-transmitted infections and unplanned pregnancies, The Independent reported.

"People may judge risks, such as whether they will regret having sex or whether they should use a condom, differently when they are drunk," researcher David Kerr, an associate professor in the School of Psychological Science at OSU, said in a statement.

Having sex without a condom is considered a risky behavior because condoms are the only way to protect against sexually transmitted infections, including HIV.

For the study, researchers collected and analyzed data from nearly 300 college students who reported their marijuana use, alcohol use, sexual activity and condom use every day for 24 consecutive days. For the purposes of the study, binge drinking was defined as four or more drinks for women and five or more drinks for men.

They found that college students were more likely to have sex on days they used marijuana.

"But we didn't find a connection between marijuana use and poor condom use," Kerr said.

The study also compared the sexual behavior of college students who were single versus those who were seriously dating someone.

"Two findings stood out," Kerr said. "Students in serious relationships had almost 90 percent of the sex reported in our study. But serious partners used a condom only a third of the time, compared to about half the time among single students. More frequent sex plus less protection equals higher risk. The stereotypical image is of college students drinking and having casual sex. That is real, but in our study it was striking how often those in serious relationships were putting their guard down."

Kerr also found that condom use was even less likely when college students used another form of birth control, an indication that they may be more focused on preventing pregnancy than on protecting themselves from an STI, he said. That's a concern because while young people may believe they are in a committed relationship, many don't end up with their college partners long-term.

"When people are in a serious relationship they may think, 'We can stop using condoms,' " Kerr said. "But if someone has unprotected sex with multiple monogamous partners over their college years, the risks can add up."

The researchers' findings, which are detailed in the Journal of Studies on Alcohol and Drugs, could be used by prevention professionals to improve sexual health messaging, identify the best times and places to distribute condoms, and encourage a focus specifically on STI prevention.

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