The prevalence of depression in inflammatory bowel disease (IBD) is significantly more than in controls. Some studies assessed the link between vitamin D and depression. The aim of this study was to assess the effect of vitamin D on Beck Depression Inventory (BDI) score in ulcerative colitis (UC) patients. In this double-blind randomized controlled trial, 90 mild to moderate UC patients were assigned to receive a single injection of 300,000 IU vitamin D3 or 1 ml normal saline as placebo. At baseline and 3 months later, measurements of BDI score and serum 25-OH-vitamin D3 were done. Data were compared by independent sample t test, Mann-Whitney U test, and analysis of covariance (ANCOVA). Baseline BDI scores were not statistically different between the two groups (p = .4); scores decreased in the vitamin D group after the intervention (p = .023). Further subgroup analysis regarding baseline serum vitamin D levels and adjusted for baseline BDIs revealed lowering effect of vitamin D on BDI scores only in subgroup with baseline serum vitamin D levels equal to or higher than 30 ng/ml (p < .001). In this study, there was a statistically significant reduction in BDI score in mild to moderate UC patients 3 months after 300,000 IU vitamin D3 injection. Subgroup analysis showed that patients with sufficient baseline vitamin D may benefit from supplementation more than vitamin D-deficient patients, which indicates that higher serum vitamin D levels may be needed for its antidepressant effect.
Keywords: BDI; IBD; depression; ulcerative colitis; vitamin D.