Lower Vitamin D Levels Are Associated With Depression in People With Chronic Spinal Cord Injury

Objectives: To determine (1) whether the serum concentration of 25-hydroxy vitamin D (25(OH)D₃) was associated with depression levels in people with chronic spinal cord injury (SCI) and (2) whether any observed association was independent of potential confounders.

Design: Cross-sectional study.

Setting: Rehabilitation institute.

Participants: Patients with chronic SCI (N=100) recruited consecutively.

Interventions: Not applicable.

Main outcome measures: Patients underwent clinical and biochemical evaluations, including assessment of 25(OH)D₃ levels and the presence and severity of depressive symptoms, by using the interviewer-assisted self-report Beck Depression Inventory-II (BDI-II).

Results: Depression (BDI-II score ≥14) was observed in 15 of 28 women (53.6%) and 18 of 72 men (25.0%) of the study population. They exhibited significantly lower 25(OH)D₃ levels, lower functional independence degree in performing activities of daily living, poorer engagement in leisure time physical activity, and higher body mass index. Lower 25(OH)D₃ levels were associated with higher BDI-II scores as well as with the occurrence of depression. These associations persisted after adjustment for all significant predictors of the BDI-II score that were selected, as possible confounders, by univariate analysis. In receiver operating characteristic analysis, a 25(OH)D₃ level of <9.99ng/mL had the highest accuracy in discriminating patients with depression.

Conclusions: In people with chronic SCI, an inverse association exists between serum 25(OH)D₃ levels and depressive symptoms, widely independent of potential confounders, especially those, peculiar to this population, that can mediate the effects of depression on vitamin D levels.