The investigators will conduct a comparative effectiveness study among Medicare Parts A, B, and D beneficiaries with inflammatory bowel disease. The investigators will compare the incidence of severe infection, bowel resection surgery, and death among new users of anti-tumor necrosis factor therapies and corticosteroids. The investigators will compute propensity scores to describe the propensity for treatment with anti-tumor necrosis factor drugs compared to corticosteroids, and will match corticosteroids and anti-tumor necrosis factor drug treated patients on the propensity score. Cox regression will be employed to assess the hazard ratio for each of the outcomes.