To many young adult couples, the status of their relationship is a little vague. In a small study, about 40 percent of young couples had differing opinions about how exclusive their relationship was, and even among those who were on the same page, about 30 percent reported having cheated

While monogamy is rare in the animal kingdom, for humans it has the practical value of being one of the easiest ways to protect against sexually transmitted diseases. Cheating and miscommunication in ostensibly exclusive relationships could trigger health issues, the study researchers say. [Top 10 Monogamous Animals]

“Couples have a hard time talking about these sorts of issues, and I would imagine for young people it’s even more difficult,” study researcher Jocelyn Warren of Oregon State University said in a statement. “Monogamy comes up quite a bit as a way to protect against sexually transmitted diseases. But you can see that agreement on whether one is monogamous or not is fraught with issues.”

The study quizzed 434 married and unmarried couples ages 18-25 about their relationships. Almost half of the couples, regardless of their marital status, disagreed as to whether or not they were seeing each other exclusively, even though they said they had discussed it. Married couples were no more likely than others to have an explicit monogamy agreement in place, and couples with children were even less likely to have an exclusivity agreement.

The only indicator of exclusivity, the researchers found, was the emotional commitment the partners reported investing in the relationship. This commitment was assessed using a scale in which participants rated themselves from 1 to 5 on statements such as "You view your relationship as permanent." Those who most strongly agreed with the statement gave themselves a 5.

With every unit increase in the commitment scale, the odds that the couple had a sustained monogamy agreement increased almost threefold, the researchers found.

Researcher Marie Harvey said in a statement that even when young adults are in a supposedly monogamous relationship, including marriage, clinicians should encourage them to engage in protected sex and reinforce the idea of using condoms. Even if the person says his or her partner is monogamous, the clinician “may want to think about advising that young person to use protection," Harvey said, since for many young adults, whether or not they know it, their relationship status remains: "It's complicated."

The researchers, whose study is to published in an issue of the Journal of Sex Research, acknowledged that research involving larger samples of individuals would be needed to confirm their findings.

This article was reprinted with permission from LiveScience.

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