Vitamin D status in patients with MS is negatively correlated with depression, but not with fatigue

Background - Depressive symptoms and fatigue are frequent and disabling symptoms of multiple sclerosis (MS). Depression and fatigue have been associated with a poor vitamin D status, and a poor vitamin D status is often found in MS. Aim - Assess whether vitamin D status contributes to depressive symptoms and fatigue in MS. Methods - Patients with MS that participated in previous studies in which depression and fatigue were assessed and of whom serum 25-hydroxyvitamin D (25(OH) D) levels were available within a timeframe of less than one half-life of 25(OH) D were included. Depression and fatigue were assessed with the Hospital Anxiety and Depression Scale and the Multidimensional Fatigue Inventory. Results - Fifty-nine patients were included. Mean scores of fatigue and depression were 14.6 (SD 4.2) and 6.2 (SD 4.4), respectively. The mean vitamin D status was 62.3 nm (SD 27.8). Vitamin D status correlated negatively with depression (r = -0.326, P = 0.006). No significant correlation was found between vitamin D status and fatigue. In a multiple regression model, vitamin D status was not a significant contributor to depression, after controlling for age Expanded Disability Status Scale score and fatigue (P = 0.078). Alternatively, depression and fatigue did not contribute to vitamin D status. Discussion - This study shows a negative correlation between vitamin D status and depressive symptoms in patients with MS. Although multiple confounders exist, we observed an indication that vitamin D status might contribute to the presence of depressive symptoms in MS. Therefore, further studies on vitamin D in MS should include depressive symptoms as outcome measures to confirm these findings