Abstract
Co-dependency is a contested construct, applied to a broad range of relational difficulties. Despite its relevance, the term remains conceptually fragmented. This limits research development and clinical recognition, hindering the creation of effective interventions. An integrative systematic review is therefore needed to consolidate recent evidence and clarify its clinical significance, aiming to synthesise conceptualisations and mental health outcomes. Following PRISMA 2020 guidelines and PROSPERO registration (CRD42024575573), Scopus, PubMed, ProQuest Central, ProQuest Dissertations & Theses Global, EBSCO, PsycINFO and PsycARTICLES were searched in September 2024 for peer-reviewed studies published between 2013 and 2024. Eligible studies addressed co-dependency's conceptualisation and/or mental health outcomes in adults. Risk of bias was assessed using MMAT and JBI for textual evidence. Thirty studies met inclusion criteria (14 quantitative, 9 qualitative and 7 theoretical). Narrative synthesis identified six conceptual perspectives: sociocultural, relational, addiction/pathology-based, developmental, psychoanalytic and cognitive-personality. Co-dependency was consistently associated with emotional distress, disrupted identity and impaired relational functioning. Two integrative frameworks are proposed: one mapping intrapersonal and interpersonal contributors to co-dependency, and one illustrating a perpetuating model of mental health outcomes. Limitations include limited cultural generalisability and the exclusion of studies addressing adjacent constructs. Strengths include methodological diversity, transparent quality appraisal and the generation of clinically relevant models. Findings support a shift towards relationally and developmentally informed understandings of co-dependency.