Studies that did not compare infliximab and adalimumab in terms of clinical outcome, efficacy, and safety; studies that did not discriminate cases of biologic-naïve ulcerative colitis from anti-TNF-exposed cases; studies that did not delineate data of patients with ulcerative colitis from those with CD; and studies involving pediatric subjects were also not included. Here, TNF is linked to ulcerative colitis.