Plasma vitamin D status and recurrent depressive symptoms in the French SU.VI.MAX cohort.

Purpose: Depression is a major public health issue because it is a common cause of disability worldwide. It has been suggested that an optimal vitamin D status may be related to fewer depressive symptoms, but findings are inconsistent. We aimed to investigate the association between plasma vitamin D at midlife and recurrent depressive symptoms and to test for a modulating effect by overall dietary quality.
Methods: The relationship between plasma 25-hydroxyvitamin D (25(OH)D) and recurrent depressive symptoms was evaluated among 1196 participants of the Supplémentation en Vitamines et Minéraux Antioxydants cohort with available data on the Center for Epidemiologic Studies-Depression Scale (CES-D) at baseline (1996-1997) and follow-up (2007-2009). Recurrent depressive symptoms were defined as a CES-D score ≥16 at baseline and follow-up. Prevalence ratios (PR) and 95 % confidence intervals (95 %-CI) were estimated using extensively adjusted Poisson regression models. Dietary quality was estimated using an index measuring adherence to the French national recommendations.
Results: Having 25(OH)D concentrations above 10 ng/mL was related to a lower probability of recurrent depressive symptoms: PR (95 %-CI) = 0.48 (0.33; 0.69); P < 0.0001). When comparing individuals with concentrations < versus ≥20 or < versus ≥30 ng/mL, no significant results were obtained. In contrast, among individuals with low dietary quality, a better vitamin D status was related to a lower probability of recurrent depressive symptoms independently of the applied cutoff.
Conclusions: Plasma vitamin D might have a preventive role against recurrent depressive symptoms, notably among individuals with poor dietary quality. Our findings are relevant for the development of depression prevention programs.