We thank O'Keefe et al for their interest in our report on the association between serum hydroxyvitamin D and current depressive symptoms.1 Lack of cardiorespiratory fitness (CRF) has been associated with depressive symptoms. For example, previous studies from the Aerobics Center Longitudinal Study found a significant inverse dose-response relationship between maximal CRF and depressive symptoms.2,3 The current study focused on depressive symptoms and their relationship to serum hydroxyvitamin D from a psychiatric perspective. Physical activity has been used as a covariate by other similar studies exploring the relationship between vitamin D and depression.4,5 In our report, we controlled for physical activity, or exercise, which represents a modifiable behavior that was statistically significant in its inverse relationship to depressive symptoms in this study.1 In sensitivity analyses that included CRF in the model, the relationship between vitamin D and depression was essentially unchanged.
We applaud O'Keefe et al's thoughtful review of the potential mechanisms linking depression, vitamin D, and cardiovascular disease. The idea that low vitamin D levels may be, in part, responsible for the association between depression and cardiovascular disorders is interesting and worthy of further investigation.
Kolade noted that guidelines for vitamin D deficiency do not call for screening vitamin D levels in the setting of current or prior depression. The idea of using vitamin D screening and, when necessary, supplementation to prevent depression relapse is very interesting and warrants further study.
Footnotes
Dr Brown has research support from the National Heart, Lung, and Blood Institute, National Institute of Mental Health, National Institute on Alcohol Abuse and Alcoholism, National Institute on Drug Abuse, the Stanley Medical Research Institute, AstraZeneca, and Sunovion.
References
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