CCL2 and central nervous system cancer: Finally, although we conducted subgroup analyses for IL‐6, IL‐8, IL‐10, and TNF‐α with glioma risk to explore the potential sources of heterogeneity, high heterogeneity still existed in the studies of IL‐4, IL‐12, IL‐17, IL‐23, TGF‐β, and MCP‐1 based on the limited number of included studies.