The association between social capital and mental health among older people living with HIV: a systematic review.

Background: Older people living with human immunodeficiency virus (HIV) constitute a vulnerable group in society and are at high risk of developing mental health problems. Although strengthening social capital is a common recommendation to reduce such mental health risks, no systematic review has examined the link between social capital and mental health among older people living with HIV. Methods: We conducted a systematic review of peer-reviewed studies examining the association between social capital and mental health among adults aged ≥50 years living with HIV. Seven databases were searched up to November 28, 2025. Studies were eligible if they quantitatively assessed at least one dimension of social capital in relation to a mental health outcome in this population. Two reviewers independently screened studies and assessed risk of bias using the Newcastle-Ottawa Scale. Owing to substantial heterogeneity, findings were synthesized narratively. Results: Among the 9,060 articles identified, 10 articles were included in this systematic review. Nine of 10 studies measured social support. Trust and civic participation were only partially captured within a broader social capital instrument in two reports from the same cohort, and reciprocity and bonding/bridging/linking capital were not measured. The instruments used to measure both social capital and mental health differed substantially across studies, and the dimensions assessed were inconsistently operationalized, which limited direct comparability of findings. Among studies measuring social support, higher levels were generally associated with lower depressive symptoms and better mental well-being, but the strength and significance of associations varied. Two reports from the same cohort assessed community/society-level social capital, reporting mixed associations. Evidence for outcomes other than depressive symptoms was sparse. Conclusion: Overall, research attention to social capital and mental health among older people living with HIV remains insufficient. Research in this field has overwhelmingly focused on social support, leaving broader dimensions of social capital largely unexamined. The available evidence suggests a beneficial association between social support and mental health, and heterogeneity in measurement instruments and operational definitions further limits comparability across studies. Future studies should devote greater attention to social capital and mental health in this population by adopting standardized and multidimensional social capital measures, and using longitudinal designs to clarify directionality. Systematic review registration: The protocol for this systematic review was registered in PROSPERO. Unique Identifier: CRD42024537839, https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=537839.