Smith KJ, et al. - The clinicians performed this meta-analysis to determine the cross-sectional and longitudinal associations of 2 inflammatory markers C-reactive protein (CRP) and Interleukin-6 (IL-6) with depression in older adults. It was found that inflammation led to depression rather than depression leading to inflammation. Notable heterogeneity was found between studies as results differed based on adjusting for confounders and on how inflammation and depression were measured. These sources of heterogeneity could explain differences in study results.