What Is the Real Impact of Smoking on Diseases Alleged to Benefit from It?

Background: Cigarette smoking is a major preventable cause of morbidity and mortality worldwide. Despite its well-known harms, epidemiological studies have reported potential protective associations between smoking and certain diseases, necessitating a critical appraisal of these claims. Summary: This review evaluates evidence on smoking's impact across eight conditions: endometrial carcinoma, rheumatoid arthritis, ulcerative colitis, Parkinson's disease, uterine leiomyoma, pre-eclampsia, COVID-19, and psychological stress. While observational data suggest inverse associations in some cases, such effects are often modest, mechanistically unclear, and confounded by biases. The review underscores the scarcity of randomized clinical trials and highlights the complexity of disentangling nicotine's biological actions from the broader toxic effects of tobacco smoke. Key Messages: The potential "protective" effects of smoking do not outweigh its well-established detrimental health consequences. Smoking cessation remains paramount, and further rigorous clinical research is needed to clarify these paradoxical findings and to explore the therapeutic potential of nicotine independent of tobacco use. .