Meta-analyses indicate significantly higher levels of interferon gamma (IFN-γ), tumor necrosis factor-α (TNF-α), C-reactive protein (CRP), interleukin 1ß (IL-1ß) and interleukin 6 (IL-6) in individuals with PTSD compared with healthy controls (Passos et al. 2015; Yang and Jiang 2020). Here, IL6 is linked to post-traumatic stress disorder.