In addition, nonparametric correlation analyses within the PTSD group revealed that PTSD symptom severity was positively correlated with the spontaneous production of IL-6 (r = .56, p = .02), and TNF-α (r = .58, p = .02), while the correlation between IL-1β and PTSD symptom severity was a trend (r = .47, p = .07). This evidence concerns the gene TNF and post-traumatic stress disorder.