Efficacy of Vitamin D Supplementation in Depression in Adults: A Systematic Review

CONTEXT: Randomized controlled trials (RCTs) investigating the efficacy of vitamin D (Vit D) in depression provided inconsistent results. OBJECTIVE: We aim to summarize the evidence of RCTs to assess the efficacy of oral Vit D supplementation in depression compared to placebo. DATA SOURCES: We searched electronic databases, two conference proceedings, and gray literature by contacting authors of included studies. STUDY SELECTION: We selected parallel RCTs investigating the effect of oral Vit D supplementation compared with placebo on depression in adults at risk of depression, with depression symptoms or a primary diagnosis of depression. DATA EXTRACTION: Two reviewers independently extracted data from relevant literature. DATA SYNTHESIS: Classical and Bayesian random-effects meta-analyses were used to pool relative risk, odds ratio, and standardized mean difference. The quality of evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation tool. RESULTS: Six RCTs were identified with 1203 participants (72% females) including 71 depressed patients; five of the studies involved adults at risk of depression, and one trial used depressed patients. Results of the classical meta-analysis showed no significant effect of Vit D supplementation on postintervention depression scores (standardized mean difference = -0.14, 95% confidence interval = -0.41 to 0.13, P = .32; odds ratio = 0.93, 95% confidence interval = 0.54 to 1.59, P = .79). The quality of evidence was low. No significant differences were demonstrated in subgroup or sensitivity analyses. Similar results were found when Bayesian meta-analyses were applied. CONCLUSIONS: There is insufficient evidence to support the efficacy of Vit D supplementation in depression symptoms, and more RCTs using depressed patients are warranted.