The association of serum 25-hydroxyvitamin D3 and D2 with depressive symptoms in childhood – a prospective cohort study

BACKGROUND   Depression in adolescence is common and early onset predicts worse outcome in adulthood. Studies in adults have suggested a link between higher total 25-hydroxyvitamin D [25(OH)D] concentrations and lower risk of depression. OBJECTIVES   To investigate (a) the association between serum 25(OH)D(2) and 25(OH)D(3) concentrations and depressive symptoms in children, and (b) whether the associations of 25(OH)D(2) and 25(OH)D(3) are different from, and independent of, each other. METHODS   Prospective cohort study with serum 25(OH)D(2) and 25(OH)D(3) concentrations measured at mean age of 9.8 years and depressive symptoms assessed with the Mood and Feelings Questionnaire by a trained interviewer at the mean ages of 10.6 years (n = 2,759) and 13.8 years (n = 2,752). RESULTS   Higher concentrations of 25(OH)D(3) assessed at mean age 9.8 years were associated with lower levels of depressive symptoms at age 13.8 years [adjusted risk ratio (RR; 95% confidence interval (CI)): 0.90 (0.86-0.95)], but not at age 10.6 years [adjusted RR (95% CI): 0.98 (0.93-1.03)] and with increased odds of decreasing symptoms between age 10.6 and 13.8 years [adjusted RR (95% CI): 1.08 (1.01-1.16)]. Serum 25(OH)D(2) concentrations were not associated with depressive symptoms. CONCLUSIONS   This is the first study in children to suggest that the association between 25(OH)D(3) concentrations and depression emerges in childhood. The association is independent of a wide range of potential confounding factors, and appears to be stronger with greater time separation between assessment of 25(OH)D(3) and assessment of depressive symptoms. Confirmation of our findings in large prospective studies and trials would be valuable.