Increased levels of interleukin (IL)-1β, tumor necrosis factor-α (TNF-α) and interleukin (IL)-18 were found in depression patients and animals (Perry et al., 2021; Yang et al., 2021), and depressive-like behaviors were ameliorated by anti-inflammatory approaches (Köhler et al., 2014). Here, IL18 is linked to major depressive disorder.