Low serum 25-hydroxyvitamin D concentrations are associated with increased likelihood of having depressive symptoms...

Accumulating evidence suggests a protective role of vitamin D against mood disorders; however, epidemiologic studies are scarce in working populations.

We investigated cross-sectionally the association of serum vitamin D status and depressive symptoms among Japanese workers.

Participants were 1786 employees (9% women), aged 19-69 y, who received health check-ups and participated in a nutrition and health survey. Serum 25-hydroxyvitamin D [25(OH)D] concentrations were measured with the use of a competitive protein binding assay. Depressive symptoms were assessed by using the Center for Epidemiologic Studies Depression (CES-D) scale. Logistic regression was used to estimate ORs with adjustment for potential confounding variables including dietary factors.

Overall, 92% of study participants had suboptimal vitamin D status [25(OH)D <30 μg/L]. Depressive symptoms were inversely associated with 25(OH)D. Compared with those with a 25(OH)D concentration of <20 μg/L, multivariable-adjusted ORs (95% CIs) for depressive symptoms (CES-D scale score ≥16) were 0.75 (0.59, 0.95) and 0.66 (0.41, 1.06) for those with a 25(OH)D concentration of 20-29 μg/L and ≥30 μg/L, respectively (P-trend = 0.01). After further adjustment for leisure-time physical activity and shift work (factors closely related to photo-initiated vitamin D production), the OR (95% CI) for the highest category of 25(OH)D was 0.70 (0.43, 1.14). The association between 25(OH)D and depressive symptoms appears to be linear, according to restricted cubic spline regression.

Results suggest that lower concentrations of circulating vitamin D are associated with increased likelihood of having depressive symptoms among apparently healthy workers.