TNF and nicotine dependence: The vital underlying pathways that exist repeatedly in three KEGG analysis results are: apoptosis – multiple species, AGE-RAGE signalling pathway in diabetic complications, IL-17 signalling pathway, TNF signalling pathway, nicotine addiction, fluid shear stress and atherosclerosis, C-type lectin receptor (CLR) signalling pathway, cocaine addiction, insulin resistance, inflammatory bowel disease (IBD) and regulation of lipolysis in adipocytes, which can be summed up as three aspects: inflammatory response, immune regulation and regulation of neurotransmission.