Abstract OBJECTIVES: Comorbid depression and anxiety are common in inflammatory bowel disease (IBD), but few population-based estimates of the burden of depression and anxiety exist. Methods to support population-based studies are needed. We aimed to test the performance of administrative case definitions for depression and anxiety in IBD and to understand what the prevalence estimated using such definitions reflects. METHODS: We linked administrative (health claims) data from the province of Manitoba, Canada with clinical data for 266 persons in the Manitoba IBD Cohort Study. We compared the performance of administrative case definitions for depression and anxiety with (a) diagnoses of depression and anxiety as identified based on the Composite International Diagnostic Interview (CIDI), which identifies disorders meeting formal diagnostic criteria, and (b) participant report of physician-diagnosed depression or anxiety. RESULTS: Administrative definitions for depression showed moderate agreement with the CIDI (κ=0.39-0.42). Agreement was higher with participant report of physician-diagnosed depression (κ=0.54). The lifetime prevalence of depression was 29.3% based on the CIDI, 17.7% based on participant report of physician-diagnosed depression, and 21.8-22.5% based on administrative data. Compared to the CIDI, administrative definitions for anxiety showed fair agreement (κ=0.21-0.25). The lifetime prevalence of anxiety was 31.2% based on the CIDI, 9.7% based on participant report of physician-diagnosed anxiety, and 24.4-31.9% based on administrative data. CONCLUSIONS: Administrative data may be used for population-level surveillance of depression and anxiety in IBD, although they will not capture undiagnosed or untreated cases.