TNF and post-traumatic stress disorder: This meta-analysis aimed to describe cytokine levels in PTSD and demonstrated that interleukin-6, interleukin-1β, interferon-γ, and tumor necrosis factor were significantly higher in patients with PTSD, as compared to controls.41 Besides, illness duration was positively associated with interleukin-1β levels, but no significant association was noted for interleukin-6 or tumor necrosis factor.41