- Smoking: Smoking status will be categorized as "nonsmoker", "smoker", or "ex-smoker", and will be considered at the time of diagnosis of IBD. Patients will be considered "smokers" if they have a smoked more than 7 cigarettes per week for at least 6 months or smoked at least 1 cigarette in the 6 months prior to diagnosis. Patients will be considered "ex-smokers" l if they quit smoking at least 6 months before diagnosis. Patients will be considered "nonsmokers" if they never smoked or did so in a very small amount or occasionally.