Associations between inflammation markers (CRP and IL-6) and depression among adolescents and young adults in Soweto and Durban, South Africa

Previous research has shown an association between inflammation and the development of depression. We examined the relationship between biomarkers of inflammation and probable depression among South African youth. We used cross-sectional data from 396 youth aged 16-24 from AYAZAZI, a cohort study (2014-2019) assessing socio-behavioural, structural, and biomedical HIV risk factors among youth. Depressive symptoms (past 7 days) were assessed using the 10-item Centre for Epidemiological Studies Depression (CES-D-10) Scale; ≥10 indicated probable depression. Inflammation was assessed using biomarkers C-Reactive Protein (CRP, in mg/L) and Interleukin-6 (IL-6, in pg/ml,) which were quantified in plasma by Enzyme-Linked Immunosorbent Assays (ELISA). CRP and IL-6 concentrations were natural log transformed standardized prior to analysis and examined as continuous measures. Multivariable logistic regression models estimated associations between measures of inflammation and probable depression, adjusting for confounders. We tested effect modification by gender and age. Among the 396 participants, 49.7% (n=197) were aged 16-18, and 59.3% (n=235) were women. Overall, 42.7% (n=169) had probable depression. CRP was associated with 32% increased odds of probable depression in adjusted models (aOR 1.32; 95% CI 1.06-1.66); no significant association was found for IL-6 (aOR 1.06; 95% CI 0.85-1.32). Gender and age did not modify the relationship between CRP or IL-6 and probable depression. Among South African adolescents and young adults, higher CRP, but not IL-6, was significantly associated with greater odds of probable depression. Findings align with growing evidence linking CRP to depression and contribute novel youth-focused data to the inflammation and mental health literature.