“People have had open marriages forever, because a lot of us would prefer to have more than one relationship. But they never end up working long-term.”

Or so says Dr. Helen Fisher, as quoted in a recent New York Times piece on the nature of open relationships. Fisher, a noted author and biological anthropologist, doubled down on this idea by claiming that the human brain isn’t equipped to juggle more than one partner at a time and that people who try to have an open relationship have “a very hard time with it” emotionally.

Fisher has made several important scientific contributions over the course of her career, and I hold a great deal of respect for her professionally. However, her claims about open relationships aren’t supported by the science — they’re just plain wrong.

Before we dive into the data, let me first say that Fisher makes a big mistake by speaking in absolute terms here. Remember: she said that open relationships never work.

In science, absolute truths like this just don’t exist because, technically, nothing is ever proven. The best we can do is speak in terms of general trends because there are almost always exceptions to the rules.

And it’s easy to find exceptions to Fisher’s claim that open relationships never work. For example, Mo’Nique, Dan Savage, and a number of other married celebrities have spoken publicly about how they’ve successfully maintained their relationships while allowing some degree of openness.

Anecdotally, it’s therefore quite clear that such relationships can work.

However, we also have scientific research backing this up—and this research finds that, on average, open relationships seem to work just as well as sexually exclusive relationships.

In a recent review of dozens of studies focusing on people who practice some form of consensual nonmonogamy (in this case, swinging, open relationships, or polyamory), researchers concluded that these folks have “similar psychological well-being and relationship quality as monogamists.”

In other words, people don’t necessarily seem to be having “a very hard time with” nonmonogamy, as Fisher suggested. Instead, people in monogamous and nonmonogamous relationships appear to be about equally happy and healthy.

Research is also inconsistent with Fisher’s claim that nonmonogamous relationships just don’t last. Although only a handful of studies have explored this idea, the available data suggest that these relationships actually do quite well over time.

For example, in a longitudinal study of 82 couples, researchers found that open marriages were statistically no more likely to end than closed marriages after a five-year period. It’s also worth noting that the vast majority of couples in both types of marriages stayed together.

In a different longitudinal study of 38 couples in open marriages, researchers found that not a single one had broken up after a two-year period.

However, I should caution that these studies were very small, and it’s possible that only people for whom open relationships were working well opted to participate. As a result, additional research is needed if we want a more reliable sense of the stability of these relationships.

I should also caution that, although research paints a pretty positive picture of open relationships, this shouldn’t be taken to mean that open relationships are right for everyone.

While some of us might be well-suited for nonmonogamy, others are probably better suited for monogamy.

Consistent with this idea, research suggests that people who have abandonment issues—or, in psychological terms, a lot of attachment anxiety—tend to be happier in their relationships to the extent that they’re monogamous.

It’s therefore important for people to choose the type of relationship that’s right for them and to not pressure their partners into an arrangement that makes them uncomfortable.

No relationship agreement—monogamy or consensual nonmonogamy—will guarantee future happiness. More important than whether you’ve agreed to have additional partners or not is whether you’ve established effective sexual communication with one another.

Being able to have open and honest conversations about sex is crucial in any type of relationship.

Despite the pessimistic claims Dr. Fisher and others have made about open relationships, research suggests that consensually nonmonogamous folks tend to be just as happy, healthy and successful when it comes to love as people who are monogamous.

Thinking about trying an open relationship but not sure where to start? I recommend checking out The Ethical Slut: A Practical Guide to Polyamory, Open Relationships, & Other Adventures for practical tips and advice on navigating communication and conflict in the world of consensual nonmonogamy.

Justin Lehmiller, PhD is a sex educator and researcher at Ball State University and author of the blog Sex and Psychology. Follow him on Twitter @JustinLehmiller.

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