Efficacy of vitamin D supplementation in depression in adults: a systematic review protocol.
BACKGROUND
The role of vitamin D in management of depression is unclear. Results from observational and emerging randomized controlled trials (RCTs) investigating the efficacy of vitamin D in depression lack consistency - with some suggesting a positive association while others show a negative or inconclusive association.


METHODS
The primary aim of this study is to conduct a systematic review of RCTs to assess the effect of oral vitamin D supplementation versus placebo on depression symptoms measured by scales and the proportion of patients with symptomatic improvement according to the authors' original definition. Secondary aims include assessing the change in quality of life, adverse events and treatment discontinuation. We will conduct the systematic review and meta-analysis according to the recommendations of the Cochrane Handbook for Systematic Reviews of Interventions. We will search the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (1966 to present), EMBASE (1980 to present), CINAHL (1982 to present), PsychINFO (1967 to present) and ClinicalTrials.gov. Unpublished work will be identified by searching two major conferences: the International Vitamin Conference, the Anxiety Disorders and Depression Conference, while grey literature will be acquired by contacting authors of included studies. We will use the random-effects meta-analysis to synthesize the data by pooling the results of included studies.


CONCLUSIONS
The results of this systematic review will be helpful in clarifying the efficacy of vitamin D supplementation and providing evidence to establish guidelines for implementation of vitamin D for depression in general practice and other relevant settings.


BACKGROUND
Unique identifier: CRD42013003849.
Department of Clinical Epidemiology & Biostatistics, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4L8, Canada.
Guowei
G
Li
Lawrence
L
Mbuagbaw
Zainab
Z
Samaan
Shiyuan
S
Zhang
Jonathan D
JD
Adachi
Alexandra
A
Papaioannou
Lehana
L
Thabane
D001008:Anxiety Disorders / Q000188:drug therapy; D003863:Depression / Q000188:drug therapy*; D003866:Depressive Disorder / Q000188:drug therapy*; D019587:Dietary Supplements; D006801:Humans; D015201:Meta-Analysis as Topic; D012107:Research Design; D000078202:Systematic Reviews as Topic; D014807:Vitamin D / Q000627:therapeutic use*; D014815:Vitamins / Q000627:therapeutic use*
D014815:Vitamins; D014807:Vitamin D