A meta-analysis by Passos et al. (2015) further substantiated that IFN-γ, interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α) are the most consistently elevated pro-inflammatory cytokines in the blood of PTSD patients compared to healthy controls [35]. This evidence concerns the gene IL1B and post-traumatic stress disorder.