Declaration of interest
There is conflicting evidence about the relationship between vitamin D deficiency and depression, and a systematic assessment of the literature has not been available.
To determine the relationship, if any, between vitamin D deficiency and depression.
A systematic review and meta-analysis of observational studies and randomised controlled trials was conducted.
One case–control study, ten cross-sectional studies and three cohort studies with a total of 31 424 participants were analysed. Lower vitamin D levels were found in people with depression compared with controls (SMD = 0.60, 95% CI 0.23–0.97) and there was an increased odds ratio of depression for the lowest v. highest vitamin D categories in the cross-sectional studies (OR = 1.31, 95% CI 1.0–1.71). The cohort studies showed a significantly increased hazard ratio of depression for the lowest v. highest vitamin D categories (HR = 2.21, 95% CI 1.40–3.49).
Our analyses are consistent with the hypothesis that low vitamin D concentration is associated with depression, and highlight the need for randomised controlled trials of vitamin D for the prevention and treatment of depression to determine whether this association is causal.
There was no dedicated funding to support this study. R.A. is supported by an Ontario Mental Health Foundation Research Training Fellowship Award, Z.S. is supported by Hamilton Health Sciences New Investigator Fund and S.M. is supported by a Canadian Institutes of Health Research New Investigator Award.
- Royal College of Psychiatrists