The mean serum levels of seven of them: TNF-α, IFN-γ, IL-2, IL-6, IL-8, IL-18, and IL-22, were significantly higher in psoriasis patients than those in controls (Figure 2, Supplementary Table 3, Supplementary Figures 1–7; TNF-α: SMD = 1.35, 95% CI 0.82 to 1.88; IFN-γ: SMD = 1.84, 95% CI 0.70 to 2.97; IL-2: SMD = 0.77, 95% CI 0.36 to 1.19; IL-6: SMD = 1.32, 95% CI 0.69 to 1.95; IL-8: SMD = 1.59, 95% CI 0.87 to 2.31; IL-18: SMD = 1.62, 95% CI 1.22 to 2.03; IL-22: SMD = 0.84, 95% CI 0.21 to 1.46). This evidence concerns the gene IL22 and psoriasis.