CCL2 and major depressive disorder: One study has shown that the presence of inflammatory cytokine interleukin-(IL)-1β correlates with agitation severity.148 Higher plasma levels of IL-6 were also associated with a higher prevalence of depression in a cohort of 69 CU or MCI individuals.149 Monocyte chemoattractant protein-1 (MCP-1) was associated with future risk of depression.150 One cross-sectional aging study found that lower vitamin B6 levels were associated with anxiety.140