IL6 and major depressive disorder: Similarly, measurements of TNF, IFN-γ, IL-6, IL-8, and IL-10 revealed no correlation between plasma and CSF levels (Ellison et al., 2005), and a meta-analysis of patients with MDD found no relationships between IL-6 or TNF levels in blood and CSF or with PET-scan markers of inflammation (Enache et al., 2019).