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

Background We 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. Methods We 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 I² statistic. Results Fifteen 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; I²=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; I²=83%) and young adults (SMD: −1.38; 95%CI: −1.65 to −1.10; p<0.001; I²=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; I²=77%). Limitations Variability in study sample sizes may affect interpretation and generalizability. Conclusions Vitamin D supplementation was associated with lower depression scores, with effects varying by subgroup.