TNF and major depressive disorder: Increased inflammatory markers, specifically C-reactive protein (CRP), interleukin (IL)-1, IL-6, and tumor-necrosis factor alpha (TNF-α), have been observed in the blood and cerebrospinal fluid (CSF) as well as in postmortem brain samples of MDD and BD patients (Enache et al., 2019; Osimo et al., 2020; Raison et al., 2006; Rosenblat et al., 2014).