TNF and psoriasis: Smoking was reported as a risk factor for TNF-antagonists-induced psoriasis,[26] which up-regulated the incidence of psoriasis, whereas some researchers suggested no significant difference between smokers and non-smokers in the incidence of psoriasis induced by TNF-antagonists.[27] Accordingly, a conclusion might be drawn that smoking acts as a major risk factor for IBD, especially for UC patients.