Post-stroke depression (PSD) has a stable prevalence of 30%. Beyond stroke severity, lesion location and prior depression, vitamin D deficiency, hyperhomocysteinaemia and insulin resistance are now recognised as independent risk factors. Mechanistically, phenotypic switching of microglia and astrocytes drives neuro-inflammation via NF-κB, JAK-STAT3 and NLRP3 inflammasome signalling. Gut-brain axis studies show reduced Faecalibacterium, increased Enterococcus and decreased short-chain fatty acids