Is depression associated with elevated levels of C-Reactive Protein, IL-1, and IL-6?
Depression is positively associated with inflammatory markers (CRP, IL-1, IL-6) in a dose-response manner, which may contribute to the cardiac risk conferred by depression.
Depression and CRP, IL-1, and IL-6 are positively associated in clinical and community samples and BMI is implicated as a mediating/moderating factor. Continuity in clinic- and community-based samples suggests there is a dose-response relationship between depression and these inflammatory markers, lending strength to the contention that the cardiac (or cancer) risk conferred by depression is not exclusive to patient populations. Available evidence is consistent with three causal pathways: depression to inflammation, inflammation to depression, and bidirectional relationships.
Howren et al. (2009) studied this question.