Interpreting the meta-analysis of efficacy of vitamin D supplementation in major depression

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Author: L. Jeyaseelan
Date: April-June 2019
From: Journal of Postgraduate Medicine(Vol. 65, Issue 2)
Publisher: Medknow Publications and Media Pvt. Ltd.
Document Type: Editorial
Length: 1,040 words
Lexile Measure: 1300L

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Byline: L. Jeyaseelan

Vellekkatt and Menon [1] have performed an interesting meta-analysis to summarize the efficacy of vitamin D supplementation in the treatment of major depression. This well-written article has included 43 clinical trial articles for systematic review, of which 4 finally qualified for further analysis. The conclusion from the meta-analysis (MA) was that the difference in depression symptom score was 0.58 units in vitamin D groups when compared with the control group. Of the four studies, one study dealt with 746 subjects out of the total 948 subjects, while the other studies dealt with roughly 200 subjects in total. Thus, one study result had dominated the results of the other studies. However, they all showed favorable result of vitamin D group over the control group.

The analysis of the effect sizes of those selected studies considered two models: fixed effect and random effects models. Under the fixed effects model, we assume that there is one true effect size and that all differences in observed effects between studies are due to sampling error. For example, multisite studies by pharmaceutical industry might like to find an average effect of few sites as they are using the same protocol. Therefore, they like to use fixed effects model. Thus, fixed effect implies that there is no sampling and the interest is restricted to selected studies only. On the other hand, random effects model allows the true effect to vary from study to study. For example, the effect size might be higher (or lower) in studies where the participants are older and so on.[2]...

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Gale Document Number: GALE|A584164896