TNF and major depressive disorder: Individuals with depression report increased levels of certain inflammatory production factors, including interleukin-6 (IL-6), tumour necrosis factor (TNF)-alpha, interleukink-10 (IL-10), as well as several soluble receptors and interleukin antagonists and cytokines, such as the soluble IL-2 receptor, IL-13 and IL-1 receptor antagonist [46,47,48].