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.