Relationship structures

The range

Monogamy — sexual and romantic exclusivity between two people. Still the most common structure, and the only one most people are taught to negotiate.

Consensual non-monogamy (CNM) — an umbrella for structures where all involved knowingly agree that romantic or sexual connections may extend beyond the couple. It is distinct from cheating in exactly one respect, and it is the decisive one: everyone knows and agrees.

• Open relationship — a primary couple with agreed outside sexual connections.
• Swinging — partnered sexual activity with others, typically together and often in social settings.
• Polyamory — multiple simultaneous romantic relationships with everyone's knowledge.
• Relationship anarchy — rejecting a fixed hierarchy between relationships; each connection defines its own terms.
• Solo polyamory — multiple relationships without a shared-household primary structure.
• Monogamish — largely monogamous with specific negotiated exceptions.

Other structures: long-distance, living apart together, asexual and aromantic relationships with negotiated intimacy, celibate partnerships, and queer-platonic partnerships.

How common

Haupert et al. (2017, Journal of Sex & Marital Therapy), analysing two US national samples totalling nearly 9,000 single adults, found roughly 1 in 5 (21 percent) had engaged in consensual non-monogamy at some point in their lives, with rates consistent across gender, race, age, education, income, religion and political affiliation. Levine et al. (2018) found around 4–5 percent of North Americans currently in a CNM relationship.

What the research finds

Comparative studies consistently fail to find CNM relationships inferior on the measures examined. Conley et al.'s reviews (2017) found no significant difference between CNM and monogamous relationships in relationship satisfaction, commitment, passion, love or jealousy across multiple samples. Rubel and Bogaert's review (2015) reached similar conclusions on psychological wellbeing.

Two findings worth stating carefully. First, several studies find CNM participants report higher rates of condom use with secondary partners and higher rates of STI testing than monogamous participants who cheat — Lehmiller (2015) found CNM individuals more likely to use barriers and get tested, and unfaithful monogamous individuals least likely. Second, stigma is documented and measurable: Conley et al. (2013) found CNM relationships rated more negatively than monogamous ones on entirely unrelated dimensions, an effect they termed the halo around monogamy.

These are correlational findings from self-selected samples. They do not show that CNM works better; they show it is not the pathology it has been assumed to be.

What makes any structure work

The research on this is more consistent than the research on structure itself.

• Explicit agreements rather than assumed ones. Most breaches involve rules that were never actually stated.
• Regular renegotiation. Agreements that worked at the start frequently need revising.
• Honesty about capacity, including time and emotional bandwidth, which are the binding constraint in polyamory far more often than jealousy.
• Sexual health agreements made explicit: barrier use with whom, testing frequency, what gets disclosed, what happens after a barrier failure or a positive result.
• Jealousy treated as information, not as a rule violation or a moral failing. It usually points at an unmet need — reassurance, time, priority — and is addressed by identifying that need.
• Not using CNM to fix a failing relationship. Opening a relationship in crisis is the most commonly cited route to it ending; opening from a stable base is a different undertaking.

Compersion — pleasure at a partner's happiness with someone else — is real for some people and not a requirement. Absence of it is not a failure.

Agreements worth writing down

Who can be involved and who cannot; what activities are in scope; safer sex requirements; disclosure timing; whether partners meet; overnight stays; social media and public visibility; time allocation; veto arrangements and what they actually mean; and what happens when someone wants to change the agreement.

Ending things

Ethical endings matter in every structure: say it directly, do not disappear, tell partners who need to know, arrange STI testing where relevant, and return belongings. In polyamorous networks a breakup affects people beyond the two involved, and giving them notice rather than leaving them to infer it is part of doing it well.

Sources

• Haupert ML et al. "Prevalence of experiences with consensual nonmonogamous relationships: findings from two national samples of single Americans." Journal of Sex & Marital Therapy, 2017.
• Conley TD et al. "Investigation of consensually nonmonogamous relationships: theories, methods, and new directions." Perspectives on Psychological Science, 2017.
• Conley TD et al. "The fewer the merrier? Assessing stigma surrounding consensually non-monogamous romantic relationships." Analyses of Social Issues and Public Policy, 2013.
• Lehmiller JJ. "A comparison of sexual health history and practices among monogamous and consensually nonmonogamous sexual partners." Journal of Sexual Medicine, 2015.
• Rubel AN, Bogaert AF. "Consensual nonmonogamy: psychological well-being and relationship quality correlates." Journal of Sex Research, 2015.
• Moors AC et al. Work on attachment and consensual non-monogamy, 2015–2021.

Last reviewed: August 2026.