23/10/2015 14:30 BST | Updated 23/10/2015 14:59 BST

People In Open Relationships Have Same STI Risk As Monogamous Couples, Study Suggests

You'd be forgiven for assuming that being in an open relationship would increase your risk of contracting a sexually transmitted infection (STI).

After all, both you and your partner may be having sex with multiple people.

But a new study has suggested couples in monogamous relationships are just as likely to contract STIs as people in consensually non-monogamous (CNM) relationships.

The study asked 556 people - 351 in a monogamous relationships and 205 in CNM relationships - about their sex lives in order to collect the data.

black couple kissing

Participants were questioned about the amount of sexual partners they have ever had, whether or not they have ever been unfaithful to a partner, what forms of contraception they use and how often they go for a sexual health check.

Around a quarter of people in monogamous relationships admitted to having sex outside of their primary relationship. The majority of people who had been unfaithful said that their primary partner did not know about their infidelity.

Despite this, CNM partners reported having more sexual partners overall than individuals in monogamous relationships.

However, the STI risk was calculated to be very similar between both groups.

"CNM partners reported taking more precautions than those in monogamous relationships in terms of greater condom use during intercourse with all partners and a higher likelihood of STI testing," the study reads.

"Thus, although persons in CNM relationships had more sexual partners, the precautions they took did not appear to elevate their rate of STIs above an imperfect implementation of monogamy."


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The study was led by Justin Lehmiller at Ball State University, Indiana, and published in The Journal for Sexual Health.

It isn't the first to suggest being in an open relationship doesn't increase STI risk.

A 2012 study from the University Of Michigan found that condom use for vaginal and anal sex was 27% and 35% lower in sexually unfaithful relationships than in open relationships.

"Monogamy can be an effective method for preventing the spread of STIs, but only if couples test negative for STIs at the start of the relationship and remain faithful while they are together," lead author Dr Terri Conley said at the time.

"If people do not find monogamy appealing or feasible, they clearly need to think about the risk this poses to their partner and consider whether an open relationship would suit their needs better, and better protect their relationship partners."

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