The relationships between depression, inflammation and self-reported disease activity in IBD and their impact on healthcare usage.

Background: Depression is common in people living with Inflammatory Bowel Disease (IBD). Depression rates increase with active disease and are linked to poorer clinical outcomes. Previous studies investigating the relationship between contemporaneous IBD disease activity and depression are often poorly controlled, use small samples and/or rely on self-reported measures of disease activity. Depression and self-reported disease activity (SRDA) are linked to increased healthcare usage, however, objective inflammation is rarely statistically controlled. The primary aim was to understand how self-reported disease activity and inflammation are related to depression. Secondary aims included assessing the relative influence of self-reported disease activity, inflammation and depression on healthcare usage.

Methods: This was a cross-sectional analysis of baseline data collected as part of a randomised controlled trial (trial registration no: ISRCTN71618461) of a digital treatment for symptom self-management in IBD (n = 599). Bivariate associations of demographic and clinical variables with depression were conducted to identify relevant covariates. Multiple linear regressions assessed (i) the relationships between depression (Patient Health Questionnaire-9 (PHQ-9)), SRDA (IBD-Control) and intestinal inflammation (faecal calprotectin (FCP)) and (ii) whether these variables explained variance in healthcare usage and economic indicators.

Results: Depression was significantly predicted by SRDA (β = -0.82, p < 0.001) but not FCP, with the model explaining 37% of the variance in depression (F(2,596) = 175.1, p < 0.001). FCP was only weakly associated with SRDA (r = -0.16, p < 0.001). Depression was independently associated with visits to primary care (β = 0.19, p < 0.001), IBD secondary care (β = 0.13, p < 0.001), IBD-related A&E attendance (β = 0.10 p < 0.05) and the impact of IBD on productivity (β = 0.24 p < 0.001) in the last 3 months.

Conclusions: Depression was related to SRDA but not FCP. Depression was also associated with healthcare usage even when SRDA and inflammation were statistically controlled. Routinely assessing and treating depression in IBD alongside managing inflammation may improve symptoms for patients and reduce healthcare costs.