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

Summary 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.