Social Determinants of the Diabetes–Depression Dyad Within a Syndemic Framework: A Scoping Review

Introduction: A syndemic is characterised by the co-occurrence, clustering, and adverse interaction of multiple diseases in populations affected by social disadvantage. The diabetes–depression dyad is increasingly examined through this lens, yet its social determinants remain fragmented and rarely translated into nursing-relevant guidance for marginalised populations. This scoping review aimed to map the structural and intermediary social factors associated with the diabetes–depression dyad within the syndemic framework and to describe how biosocial interaction has been conceptualised and operationalised. Methods: Following the Joanna Briggs Institute methodology and reporting using PRISMA-ScR, we searched Scopus, Web of Science, PubMed, ScienceDirect, CINAHL, PsycINFO, Embase and Google Scholar up to 20 September 2026, with no restrictions on language, design, or year. We interpreted findings using an adapted VIDDA framework aligned with the WHO model of Social Determinants of Health. Results: Thirty-five publications (2012–2026) were included. Structural violence, poverty, displacement and migration were the most frequently reported structural determinants, whereas access to health services, neighbourhood conditions and interpersonal abuse were the most frequent intermediary factors. Biosocial interaction was formally tested in only a minority of studies, mainly through additive or multiplicative models; most publications documented co-occurrence or association rather than demonstrated synergy. Conclusions: Social determinants are central to the diabetes–depression syndemic in vulnerable groups, yet the evidence remains conceptually rich but empirically uneven, with few studies formally testing biosocial interaction. For nursing practice, these findings support pairing routine glycaemic and mood assessment with structured screening for social needs, coordinating integrated care, and delivering culturally safe, person-centred support. The included studies did not directly evaluate whether such nurse-led, socially informed care reduces health inequities; longitudinal and interventional research is needed to test this.