IL1B and major depressive disorder: Animal studies have shown that mice subjected to a model of depression display increased levels of interleukin-1ß in the hippocampus (Goshen et al., 2008), a brain region integral to the neuropathology of PTSD due to its role in fear learning and contextual processing (Maren et al., 2013), as well as memory formation and retrieval (Bremner et al., 1997); in fact, a recent study in post-mortem human brain observed increased IL1B expression in dlPFC of PTSD cases compared to controls (Girgenti et al., 2021).