Adult attachment in consensual non-monogamy: a systematic review of methodological trends and challenges

Consensual non-monogamy (CNM)—a relational model in which individuals engagein multiple romantic or sexual partnerships with mutual consent—challenges traditionalmonogamy-based frameworks in psychological research, particularly in the study of adultattachment. This systematic review aimed to identify methodological trends, limitations,and future directions in attachment research on CNM populations. Following PRISMAguidelines, 13 studies published between 1970 and 2025 were identified through comprehensivedatabase searches and reference screening. Most studies employed cross-sectional,quantitative designs and used monogamy-oriented attachment instruments such as the Experiencesin Close Relationships-Revised (ECR-R) and its short form (ECR-S). Whilethese tools often demonstrated strong internal reliability, few studies assessed their validityin CNM contexts. Sampling was predominantly convenience-based and skewed towardWhite, Western, and LGBTQ+ participants, limiting generalizability. Findings alsohighlighted a lack of longitudinal and mixed-methods approaches, with only one qualitativestudy offering deeper insight into relational processes. This review concludes thatfuture research should prioritize developing CNM-specific attachment measures, expanddemographic diversity, and adopt longitudinal and qualitative designs to better capture thecomplexity of attachment in diverse relationship structures.