Vitamin D and depression

•There is adequate evidence for a positive association between vitamin D deficiency and depression.•If a depressed individual is deficient, Vitamin D supplementation/augmentation can be an effective treatment.•The current evidence base is limited by methodological flaws.•There is a need for further randomised controlled longitudinal studies.

ObjectiveTo examine whether vitamin D deficiency or insufficiency is associated with depression and whether vitamin D supplementation is an effective treatment for depression.MethodEmpirical papers published in recent years were identified using three search engines and online databases - PubMed, Google Scholar and Cochrane Database. Specific search terms used were 'vitamin D', 'depression' and 'treatment' and articles were selected that examined the association between vitamin D deficiency/insufficiency and depression, vitamin D supplementation and Vitamin D as a treatment for depression. Our review weighted more recent studies (from 2011), although also considered earlier publications.ResultsEmpirical studies appear to provide increasing evidence for an association between vitamin D insufficiency and depression, and for vitamin D supplementation and augmentation in those with clinical depression who are vitamin D deficient. Methodological limitations associated with many of the studies are detailed.LimitationsArticles were restricted to those in the English language while publication bias may have weighted studies with positive findings.ConclusionsThere remains a need for empirical studies to move beyond cross-sectional designs to undertake more randomised controlled longitudinal trials so as to clarify the role of vitamin D in the pathogenesis of depression and its management, as well as to establish whether currently suggested associations are clinically significant and distinctive.