Similarly, peripherally administered IFN-α is capable of accessing the brain in humans and is associated with an inflammatory response in the CNS as reflected by elevations in cerebrospinal fluid (CSF) IL-6, MCP-1 and with decreases in the 5-HT metabolite, 5-HIAA, which, in turn, were correlated with depression [56]. Here, CCL2 is linked to depressive disorder.