IL6 and major depressive disorder: Numerous studies conducted on patients meeting the criteria of the Diagnostic and Statistical Manual of Mental Disorders (DSM) [56] for major depression have found significant increases in plasma or serum levels of CCL2, IFNγ, IL-1α, IL-1β, IL-2, IL-6, IL-8, IL-12 and TNF-α, together with CRP [46,57].