Vitamin D supplementation to reduce depression in adults: meta-analysis of randomized controlled trials

Abstract Objective: To estimate the weighted mean effect of vitamin D supplementation in reducing depressive symptoms among the adults aged 18 years or older diagnosed with depression or depressive symptoms. Method: Meta-analysis of randomised controlled trials (RCTs) in which vitamin D supplementation was used to reduce depression or depressive symptoms was conducted. Databases MEDLINE, EMBASE, psych INFO, CINAHL plus and Cochrane library were searched from inception to August 2013 for all publications on vitamin D and depression regardless of language. The search was further updated until May 2014 to include further studies being published. Studies involving adults 18 years and over, diagnosed with depressive disorder based on both the Diagnostic and Statistical Manual (DSM) of Mental disorders or other symptom checklist for depression were included. Meta-analysis was performed using random-effects due to differences between the individual RCTs. Results: Nine trials with a total of 4923 participants were included in the analysis. There was no significant reduction in depression following vitamin D supplementation (SMD= 0.28 95 CI -0. 14, 0.75, p= 0.19) However, most of the studies focused on individuals who had low level of depression and sufficient serum vitamin D at baseline. The included studies used different vitamin D dose with a varying degree of intervention duration. Conclusion: Future RCTs examining the effect of vitamin D supplementation among individuals who are both depressed and vitamin D deficient are needed.