What is the role of Vitamin D in depression?

The evidence for a cross-sectional association between vitamin D deficiency and depression is weak. • Cohort studies of vitamin D deficiency showed an increased risk of depression at follow-up. • Oral supplements of vitamin D showed no effect on depression symptoms. • The quality of evidence for vitamin D and depression is poor. • Well-designed, large clinical trials are needed to understand the effects of vitamin D on depression.