Postpartum and Youth Depression in the Context of Vitamin D Supplementation: Systematic Review and Meta-analysis

BackgroundWe conducted a systematic review and meta-analysis to assess the effect of vitamin D supplementation on depression among adolescents and young adults compared with placebo and baseline. MethodsWe searched databases and reference lists from inception to May 2024 for English-language studies, including cohort studies, case studies, and randomized clinical trials. Study quality was assessed using the Cochrane RoB2 tool and the Newcastle-Ottawa Scale. Random-effects meta-analyses estimated the standardized mean difference (SMD) in depression scores (primary outcome) and anxiety scores (secondary outcome). Heterogeneity was assessed using the I{superscript 2} statistic. ResultsFifteen studies (2010-2024) from 7,638 citations met inclusion criteria. The mean sample size was 5,271 (range: 38-74,840). Meta-analysis of nine studies showed that vitamin D supplementation significantly reduced depression scores versus placebo (SMD: -0.43; 95%CI: -0.75 to -0.12; p=0.007; I{superscript 2}=78%). Of six studies not included in the meta-analysis, five reported significant associations between supplementation and lower depression. Subgroup effects were observed for postpartum women (SMD: -0.55; 95%CI: -1.04 to -0.06; p<0.05; I{superscript 2}=83%) and young adults (SMD: -1.38; 95%CI: -1.65 to -1.10; p<0.001; I{superscript 2}=76%). Meta-analysis of four studies found no significant association with anxiety (SMD: -0.31; 95%CI: -0.75 to 0.12; p=0.16; I{superscript 2}=77%). LimitationsVariability in study sample sizes may affect interpretation and generalizability. ConclusionsVitamin D supplementation was associated with lower depression scores, with effects varying by subgroup.