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

Objectives: The aim of this study was to estimate the weighted mean effect of vitamin D supplementation in reducing depressive symptoms among individuals aged ≥18y diagnosed with depression or depressive symptoms. Methods: A meta-analysis of randomized 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 the 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 to May 2014 to include newer studies being published. Studies involving individuals aged ≥18y who were diagnosed with depressive disorder based on both the Diagnostic and Statistical Manual of Mental Disorders or other symptom checklist for depression were included. Meta-analysis was performed using random effects model due to differences between the individual RCTs. Results: The analysis included nine trials with a total of 4923 participants. No significant reduction in depression was seen after vitamin D supplementation (standardized mean difference=0.28; 95% confidence interval, -0.14 to 0.69; P=0.19); however, most of the studies focused on individuals with low levels of depression and sufficient serum vitamin D at baseline. The studies included used different vitamin D doses with a varying degree of intervention duration. Conclusions: Future RCTs examining the effect of vitamin D supplementation among individuals who are both depressed and vitamin D deficient are needed.