Several studies have reported elevated TNFα levels in the blood and cerebrospinal fluid in patients with MDD (Dowlati et al., 2010; Goldsmith et al., 2016; Huang & Lee, 2007; Liu et al., 2012; Martinez, Garakani, Yehuda, & Gorman, 2012; Stelzhammer et al., 2011), but this finding was questioned in a recent meta‐analysis (Anisman et al., 1999). This evidence concerns the gene TNF and major depressive disorder.