TNF and major depressive disorder: In a third of patients with depression, the serum and cerebrospinal fluid (CSF) concentrations of inflammatory markers in serum showed the elevation of pro-inflammatory factors such as interleukine (IL)-6, tumor necrosis factor (TNF)-α, and C-reactive protein compared to non-depressed patients (Raison et al., 2006; Dantzer et al., 2008; Dowlati et al., 2010; Liu et al., 2012).