Mental Health Disorders in Patients with Inflammatory Bowel Disease Onset in Childhood or Youth – A Nationwide Cohort Study from Denmark

Purpose: The study aims to explore the association between patients diagnosed with inflammatory bowel disease (IBD) in childhood or youth and mental health disorders. Methods: The study is a register-based cohort study of patients with IBD-onset before 25 years of age and matched references. They were followed until 30 years of age. The incidence rate and incidence rate ratio (IRR) for a wide spectrum of mental health disorders were assessed based on diagnostic codes from the Danish National Patient Registry, reimbursed prescriptions for psychotropic medications, and composite measures combining diagnosis and medication. Furthermore, the relative excess risk due to interaction (RERI) for parental educational level and parental mental health disorders were estimated. Results: A total of 4904 patients with Crohn's disease (CD), 5794 with ulcerative colitis (UC), and 94,802 matched references were identified. Patients with CD-onset before age 18 had a higher risk of anxiety disorders (IRR 1.58 (CI95%: 1.33-1.86)), while patients with CD-onset between age 18 to 24 had a higher risk of both anxiety and mood disorders. Patients with UC-onset before age 18 had a higher risk of anxiety disorders (IRR: 1.39 (CI95%: 1.19-1.64)). In general, patients with IBD had a higher risk of receiving psychotropic medication. Parental education had a subadditive interaction with the risk of emotional disorders for both patients with CD and UC, while maternal mental health disorders had a subadditive interaction for patients with UC. Conclusion: Patients with CD and UC have a higher risk of mental health disorders, primarily due to an elevated risk of emotional disorders and a higher use of psychotropic medication. Surprisingly, the study demonstrated subadditive effect of parental education and for patients with UC maternal mental health disorders on the risk of emotional disorders.