Meta-analyses have associated traumatic experiences with higher levels of pro-inflammatory interleukin 6 (IL-6), interleukin 1β (IL-1β), and tumor necrosis factor α (TNF-α)5, and have found PTSD to be associated with higher levels of IL-6, IL-1β, and interferon γ (IFN-γ), but not TNF-α11. This evidence concerns the gene IFNG and post-traumatic stress disorder.