Vitamin D and Postpartum Depression: A Narrative Review.

Background/objective: Postpartum depression (PPD) is a significant public health issue affecting about 19% of mothers globally. It has well-documented impacts on maternal well-being, mother-infant relationships, and child developmental outcomes. At the same time, the level of vitamin D deficiency in women of reproductive age is very high (affecting 60-87 percent of pregnant women globally). The review aims to synthesize current evidence and highlight priority research areas to improve maternal mental health outcomes. Methods: A systematic literature search of PubMed, Scopus, and Google Scholar (2015-2026) was conducted, followed by narrative synthesis of mechanistic, observational, and interventional evidence. Results: Adequate vitamin D status may contribute to a reduced risk of postpartum depression through multiple interacting pathways, including serotonin synthesis and metabolism (via tryptophan hydroxylase 2 (TPH2) and monoamine oxidase-A (MAO-A) regulation), neuroplasticity via brain-derived neurotrophic factor (BDNF) signaling, and suppression of the pro-inflammatory cytokine cascade. Dose-response meta-analyses and large prospective cohort studies indicate consistent negative relationships between maternal vitamin D levels and postpartum depressive and anxiety symptoms with optimal serum 25-hydroxyvitamin D (25(OH)D) levels of 90-110 nmol/L. Conclusions: There is still limited evidence on the intervention; it is still methodologically diverse, and only a few randomized controlled trials have been carried out on specifically postpartum populations.