Additionally, depression caused by CRS may be related to inflammatory pathways, including tumor necrosis factor (TNF) signaling pathway, nuclear factor κB (NF-κB) signaling pathway and Toll-like receptor signaling pathway (Wang et al., 2017), which indicates inflammatory and microglial activation are involved in depressive-like behaviors (Yamawaki et al., 2018). Here, TNF is linked to major depressive disorder.