People in monogamous relationships catch sexually transmitted diseases just as often as those in open relationships, a new survey suggests, largely due to infidelity spreading infections.

Reported in the current Journal of Sexual Medicine, the survey of 554 people found that monogamous couples are less likely to use condoms and get tested for STDs — even when they're not being faithful to their partner.

“It turns out that when monogamous people cheat, they don’t seem to be very good about using condoms,” Justin Lehmiller, a psychologist at Ball State University and author of the study, told BuzzFeed News by email. “People in open relationships seem to take a lot of precautions to reduce their sexual health risks.”

The finding matters because people who think they are in monogamous relationships may face higher odds of an infection than they suspect, Lehmiller and other researchers told BuzzFeed News. And a stigma around open relationships that views such couples as irresponsible — even among researchers who conduct studies — may be skewing the evidence.

One in four of the 351 monogamous-relationship participants in Lehmiller’s survey said they had cheated on their partners, similar to rates of sexual infidelity reported in other surveys. About 1 in 5, whether monogamous or not, reported they had been diagnosed with an STD. Participants averaged between 26 to 27 years old, and most (70%) were women.

For people in supposedly exclusive relationships, Lehmiller said, “this risk is compounded by the fact that cheaters are less likely to get tested for (STDs), so when they pick something up, they are probably less likely to find out about it before passing it along.”

Psychologist Terri Conley of the University of Michigan told BuzzFeed News that the survey results echoed her team’s findings in a 2012 Journal of Sexual Medicine study that found people in open relationships were more likely to use condoms correctly in sexual encounters than people in exclusive relationships.

To bolster confidence in the results, Conley said, more funding is needed to test research subjects for STDs directly, rather than relying on their own notoriously unreliable self reporting of infections.

She compared just assuming that monogamous relationships are safer to assuming abstinence education will really stop teenagers from having sex: “Sure, abstinence would be great, but we know that isn’t reality.”

To put it another way, Lehmiller said, “there’s a potential danger in monogamy in that if your partner puts you at risk by cheating, you’re unlikely to find out until it’s too late.”

Sex researchers don’t want to criticize monogamy, Conley added, making funding a definitive study more difficult.

In a commentary on Lehmiller’s study in Journal of Sexual Medicine, Conley argued that sex researchers are “committed to the the belief that monogamy is best” and are “reluctant to consider contradictory evidence.”

“I’m not saying monogamy is bad,” Conley said. “What I found is that the level of hostility among reviewers to suggesting people in consensual non-monogamous relationships are more responsible is really over the top.”

Conley said she initially struggled to publish her 2012 study. When she changed the framing of its conclusion to find that “cheaters” in monogamous relationships were more irresponsible, the study was suddenly published.

“Even in a scientific review process, challenging researchers’ preconceived notions is perilous,” she wrote in her commentary.

Other relationship researchers disagree, however, saying that sociologists have cast shade on monogamy — finding declines in happiness, sexual satisfaction, and frequency of intercourse — for decades. “This is about as widespread a finding as one gets,” Harry Reis, a psychologist at the University of Rochester, told BuzzFeed News. He called the idea that social scientists are biased against studies showing the value of non-monogamous relationships was “poppycock.”

Sex researcher Debbie Herbernick of Indiana University echoed this view, saying funding is not an issue: “I've never seen much negative reaction or pushback.”

More critically, Reis said, reviewers might be dubious about the data collected on open relationships, given their relative rarity making reliable data collection difficult.

Although Lehmiller published his study, he agreed with Conley that a stigma still marks open relationships, even in science. “People, including many sex researchers," he said, "have a tendency to put monogamy on a pedestal and to be very judgmental when it comes to consensual non-monogamy."