TNF and central nervous system cancer: The overall analysis showed that increased circulating interleukin‐6 (IL‐6) [SMD 0.81 (95% CI: 0.21‐1.40; P = .008)], interleukin‐8 (IL‐8) [SMD 1.01 (95% CI: 0.17‐1.84; P = .018)], interleukin‐17 (IL‐17) [SMD 1.12 (95% CI: 0.26‐1.98; P = .011)], tumor necrosis factor‐α (TNF‐α) [SMD 1.80 (95% CI: 1.03‐2.56; P = .000)], transforming growth factor‐β (TGF‐β) [SMD 10.55 (95% CI: 5.59‐15.51; P = .000)], and C‐reactive protein (CRP) [SMD 0.95 (95% CI: 0.75‐1.15; P = .000)] levels were significantly associated with glioma risk.