The association between inflammatory bowel disease and mental ill health: A retrospective cohort study using data from UK primary care

Background: Patients with active inflammatory bowel disease (IBD) and mental illnesses experience worse IBD outcomes. Aim: To describe the incidence of mental illnesses, including deliberate self-harm, in IBD patients. Methods: A population-based retrospective cohort study using IQVIA medical research data of a primary care database covering the whole UK, between January 1995 and January 2021. IBD patients of all ages were matched 4:1 by demographics and primary care practice to unexposed controls. Following exclusion of patients with mental ill health at study entry, adjusted hazard ratios (HR) of developing depression, anxiety, deliberate self-harm, severe mental illness and insomnia were calculated using a Cox proportional hazards model. Results: We included 48,799 incident IBD patients: 28,352 with ulcerative colitis and 20,447 with Crohn's disease. Incidence rate ratios of mental illness were higher in IBD patients than controls (all p < 0.001): deliberate self-harm 1.31 (95% CI 1.16-1.47), anxiety 1.17 (1.11-1.24), depression 1.36 (1.31-1.42) and insomnia 1.62 (1.54-1.69). Patients with Crohn's disease were more likely to develop deliberate self-harm HR 1.51 (95% CI 1.28-1.78), anxiety 1.38 (1.16-1.65), depression 1.36 (1.26-1.47) and insomnia 1.74 (1.62-1.86). Patients with IBD are at increased risk of deliberate self-harm (HR 1.20 [1.07-1.35]). The incidence rate ratios of mental illnesses were particularly high during the first year following IBD diagnosis: anxiety 1.28 (1.13-1.46), depression 1.62 (1.48-1.77) and insomnia 1.99 (1.78-2.21). Conclusion: Deliberate self-harm, depression, anxiety and insomnia were more frequent among patients with IBD. IBD is independently associated with an increased risk of deliberate self-harm.