Interleukin-6 is a strong biomarker and predictor for the development of depression and dementia.
"Now, interleukin-6 is one of the best predictors of conditions like depression and dementia. It is one of the most prototypical inflammatory molecules." (said at 0:20:29)
Interleukin-6 (IL-6) is a well-established pro-inflammatory cytokine associated with neuroinflammation, but describing it as 'one of the best predictors' or a 'strong biomarker' for the onset of depression and dementia overstates its predictive power. Systematic reviews and meta-analyses of prospective longitudinal studies show that while elevated IL-6 levels are statistically significantly associated with future depressive symptoms and cognitive decline, the effect sizes are modest (e.g., correlation coefficients r < 0.10 for depression; odds ratios around 1.34 for cognitive decline). IL-6 alone possesses limited individual diagnostic or predictive utility compared to established risk factors and disease-specific biomarkers (such as APOE ε4 status, amyloid-beta, and tau for Alzheimer's disease).
- partial: CRP, IL-6 and depression: a systematic review and meta-analysis of longitudinal studies. (Journal of affective disorders 2013)
"Raised inflammatory markers have a small but significant association with the subsequent development of depressive symptoms. This is a robust effect which remains significant after adjustment for age and a wide range of factors associated with risk for depression." (abstract, conclusions, passage verified)
pubmedfull study (doi) - partial: The longitudinal associations of inflammatory biomarkers and depression revisited: systema… (Molecular psychiatry 2021)
"Small, prospective associations of depression and inflammatory biomarkers are observed in both directions, particularly for IL-6; however, the strength and importance of this relationship is likely obscured by the heterogeneity in depression and profound study/methodological differences." (abstract, results, passage verified)
pubmedfull study (doi) - partial: Association of inflammation and cognition in the elderly: A systematic review and meta-ana… (Frontiers in aging neuroscience 2023)
"The data from longitudinal studies suggested that levels of IL-6 significantly increased the risk of cognitive decline [OR = 1.34, 95% CI (1.13, 1.56)]. However, intermediate levels of IL-6 had no significant effect on the final clinical endpoint [OR = 1.06, 95% CI (0.8, 1.32)]." (abstract, results, passage verified)
pubmedfull study (doi)