Smoking is generally considered horrible for your health. There are too many studies to cite here. However, in doing some research on IBDs (Inflammatory Bowel Diseases), it has been shown that while smoking is bad for people who suffer Crohn’s Disease, it has been demonstrated to be a positive for people with Ulcerative Colitis. Additionally, it helps prevent the disease. One study explaining this with other citations to other studies can be found here https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2014383/

It should be noted, however, that the likely main positive factor is simply the nicotine (not the other harmful chemicals in smoke), which is hypothesized to increase mucus production in the colon as well as suppress the immune system (IBDs are auto-immune disorders).

While I am not a doctor and this is based solely on my own amateur research, my strong sense is that the side effects of smoking GREATLY outweigh any benefits of helping prevent and control this one relatively rare disease.