What Is Consensual Non-Monogamy? Modern Love, Many Forms

By Mark Ryan, BACP Accredited Psychotherapist and NCPS Accredited Relationship Therapist

People often bring the phrase “non-monogamy” into a first session as though it names one thing. It doesn't. Open relationships, polyamory, swinging, relationship anarchy, and the quieter, more private arrangements couples build without ever naming them publicly, all get folded under the same umbrella, and the differences between them matter far more than the umbrella term suggests. Some of what follows will be familiar if you already practise some form of non-monogamy. Some of it is for people who are only just wondering whether monogamy, as currently arranged, is the right shape for them. Both are welcome here.

A short, honest history

Monogamy as romantic destiny is a newer idea than it looks. For most of recorded history, marriage was an economic and political arrangement rather than an emotional one; love, where it appeared, was treated as a fortunate accident rather than the point of the exercise (Coontz, 2005). Romantic love only became a socially acceptable reason to marry in the eighteenth and nineteenth centuries, and even then, it arrived bundled with rigid roles about who earned and who cared. For much of that history, marriage also functioned as a means of controlling women specifically, restricting their sexuality, labour, and property through the marriage contract itself. None of this is presented to score a point against marriage; the version of monogamy most of us inherited as “natural” is simply a recent social invention, not a timeless default that non-monogamy deviates from.

The twentieth century moved things again: women's growing financial independence, the feminist challenge to the idea that marriage alone should fulfil a woman's life, and the long fight for the legitimacy of queer relationships all reshaped what a relationship was assumed to require. What we're seeing now is arguably a continuation of that same trajectory rather than a break from it: people increasingly building the relationship structure that suits them, rather than accepting the one they were handed.

What “non-monogamy” covers

Consensual non-monogamy, usually shortened to CNM, is the umbrella term researchers use for any relationship structure where everyone involved has agreed, knowingly and honestly, to more than one romantic or sexual connection. It is worth separating this clearly from cheating, which involves no such agreement; the word doing the real work in CNM is consensual, not non-monogamous. Underneath that umbrella sit several distinct structures, and I find couples do better once they stop treating them as interchangeable.

Open relationships typically involve a primary couple who agree that one or both may have sex outside the relationship, usually without romantic attachment forming as part of the arrangement. Polyamory goes further, explicitly making room for additional loving, committed relationships alongside the original one, sometimes arranged hierarchically around a primary partnership and sometimes deliberately non-hierarchical, with no relationship ranked above another. Swinging typically centres on shared sexual experiences, often with both partners present. Relationship anarchy rejects the idea of a hierarchy of relationship types altogether, treating friendships, romantic partnerships, and everything between as worthy of the same care and negotiation rather than automatically subordinate to a “main” relationship. None of these is a stepping stone to the others, and none is more legitimate than the rest; they are different answers to the same underlying question of how people want to structure love, sex, and commitment.

Monogamy is a choice too

One assumption sits underneath most of this conversation, and it deserves saying directly: monogamy is a relationship structure, not the default that other structures deviate from. For a great many couples, monogamy was never actively discussed, chosen, or agreed to; it was simply assumed, because it's the arrangement built into most inherited scripts about what a relationship is meant to look like. Treating it as the safe, unremarkable option, while any other structure is the one that has to justify itself, gets this backwards. Monogamy is just as much a choice as polyamory or an open relationship, and couples who have never actually discussed it as one are often standing on ground that is less solid than it looks.

It also isn't as airtight as its reputation suggests. Meta-analytic research puts the lifetime rate of sexual infidelity in marriage at around 20 to 25 percent (Fincham and May, 2017), and there's good reason to think that figure is conservative rather than exaggerated: one study found infidelity reported anonymously via computer was roughly six times higher than the same question asked face to face (Whisman and Snyder, 2007). A meaningful share of relationships that consider themselves monogamous are, in practice, functioning as non-consensually non-monogamous: sex or emotional connection happening outside the relationship without the other partner's knowledge or agreement. None of this is an argument against monogamy, which remains a completely legitimate and often excellent choice. It's an argument against treating monogamy as though it doesn't require the same honesty, and the same active choosing, that any other relationship structure does.

What I see when couples are considering opening up

Couples rarely arrive at this decision from a position of total calm, and I want to say plainly that this is normal rather than a warning sign. Someone has usually been carrying a want, sometimes for years, before finally naming it; a fantasy about non-monogamy, a friendship that has started to feel like more, a simple curiosity about whether monogamy was ever actually chosen or just assumed. The other partner is often somewhere between curious and frightened, sometimes both in the same conversation. What I find myself doing most in this early stage is slowing the couple down before any agreement gets made, because the agreements that hold up are the ones built on real clarity about what each partner wants, not agreements built to manage one partner's anxiety or satisfy the other's urgency.

One honest pattern: couples sometimes open up in the hope that it will fix something already wrong in the relationship, a dwindling sex life, a sense of distance, boredom that has crept in unnoticed. Non-monogamy can be a wonderful choice for a relationship that is already fundamentally secure, but it rarely repairs one that isn't, and it tends to magnify whatever was already fragile rather than resolve it. Part of my work with couples at this stage is helping them tell the difference between opening up towards something they both genuinely want and opening up away from a problem they haven't yet named.

Consensual non-monogamy (CNM) is an umbrella term that covers a range of relationship styles

What the research shows

There's a persistent assumption, inside and outside therapy rooms, that non-monogamous relationships must be less stable, less satisfying, or less psychologically healthy than monogamous ones. The research does not support this. A systematic review examining decades of comparative studies found no evidence that monogamy affords people superior relationship outcomes compared with consensual non-monogamy; where differences appeared, they tended to favour CNM couples on measures like jealousy management and communication, likely because these couples are forced to have explicit conversations that monogamous couples are culturally permitted to skip (Conley, Matsick, Moors and Ziegler, 2017). A more recent scoping review reached a similar conclusion: across the available research, CNM relationships show broadly comparable relationship functioning to monogamous ones, and where CNM-specific distress appears, it tends to trace back to external stigma and internalised shame about the relationship structure itself, rather than anything intrinsic to non-monogamy (Gupta et al., 2024).

That last point matters clinically. Much of the distress I see in CNM clients isn't produced by the relationship structure; it's produced by the world's reaction to it, and by having internalised some of that reaction before ever walking into a therapy room.

Why having an affirming therapist matters

Research into CNM clients' experience of therapy has found a consistent and troubling pattern: therapists frequently default to monogamous assumptions, treat the relationship structure itself as the presenting problem, or subtly imply that “real” commitment requires exclusivity, and clients notice this immediately (Moors, 2022). People in CNM relationships are also more likely to identify as LGBTQ+ than the general population, which means many clients are navigating overlapping layers of stigma at once, about their relationship structure and their sexual or gender identity, often while trying to find a single therapist competent in both. An affirming therapist doesn't need to personally understand the appeal of non-monogamy any more than a good doctor needs to share a patient's diet. What is required is the discipline to treat your relationship structure as a fact to be understood rather than a symptom to be corrected, and to bring the same curiosity to a polycule that I would bring to any couple.

Where jealousy fits into all of this

Jealousy comes up in nearly every conversation I have about non-monogamy, understandably, and it deserves more room than a paragraph here can give it. I've written about it at greater length elsewhere: what jealousy actually is and how it behaves generally, here, the particular experience of living alongside a jealous partner, here, and the patterns specific to non-monogamous relationships, including the difference between compersion and its absence, and what happens when one partner wants sex without love while the other wants love too, here. If jealousy is the reason you're reading this, those three pieces will serve you better than anything I could add in summary.

Structure, agreements, and what tends to work

Couples who build lasting non-monogamous arrangements tend to share a few habits rather than a particular structure. They revisit their agreements deliberately rather than assuming an early conversation still holds a year later; needs and boundaries shift and treating an agreement as permanent because it was once agreed is a common source of quiet resentment. They also tend to be specific rather than aspirational: “we'll figure it out as we go” sounds flexible but often means neither partner has said what they need, whereas naming concrete boundaries, however unglamorous, gives both people something to hold onto when a difficult moment arrives. And couples who choose hierarchical structures, where one relationship is explicitly prioritised, tend to do best when they are honest that hierarchy carries a real cost for whoever holds the lower position, rather than assuming goodwill alone will absorb it (Flicker, Sancier-Barbosa, Moors and Browne, 2021).

None of this is about finding the one correct way to do non-monogamy, because there isn't one. It's about being specific enough with each other that the relationship you've agreed to is the relationship you're both living.

Where therapy fits

I work with couples, polycules, and individuals across the full range of relationship structures, and I don't come to that work trying to move anyone towards monogamy or away from it. Some of the couples I see are considering opening up for the first time and want a space to think it through honestly before making any changes. Others have been practising CNM for years and are working through something specific, jealousy, a hierarchy that no longer feels fair, an agreement that needs renegotiating, rather than the structure itself. Both are ordinary reasons to come to therapy, and neither requires you to justify your relationship shape before we get to the actual work.

If you'd like to talk any of this through, I offer a free 30-minute consultation, in person in London or by video.

About the Author

Mark Ryan is a BACP Accredited Psychotherapist and NCPS Accredited Relationship Therapist working in person across central London, from rooms in Pimlico, Kensington, and Angel. He works with couples, individuals, and polycules on relationship issues including jealousy, affairs and betrayals, sex problems, and considered separation. His practice is integrative, sex-positive, and affirming of all relationship structures and identities.

References

Coontz, S. (2005). Marriage, a History: How Love Conquered Marriage. Penguin Books.

Conley, T. D., Matsick, J. L., Moors, A. C., & Ziegler, A. (2017). Investigation of consensually nonmonogamous relationships: Theories, methods, and new directions. Archives of Sexual Behavior, 47, 1177–1195. https://link.springer.com/article/10.1007/s10508-018-1286-4

Gupta, K., et al. (2024). A scoping review of research on polyamory and consensual non-monogamy: Implications for a more inclusive family science. Journal of Family Theory & Review. https://onlinelibrary.wiley.com/doi/full/10.1111/jftr.12546

Moors, A. C. (2022). Stigma toward consensual non-monogamy: Thematic analysis and minority stress. Archives of Sexual Behavior.

Flicker, S. M., Sancier-Barbosa, F., Moors, A. C., & Browne, L. (2021). A closer look at relationship structures: Relationship satisfaction and attachment among people who practice hierarchical and non-hierarchical polyamory. Archives of Sexual Behavior, 50(4), 1401–1417. https://doi.org/10.1007/s10508-020-01875-9