These factors have been linked to hippocampal atrophy in MDD15–17, with reduced levels of brain-derived neurotrophic factor (BDNF) and fibroblast growth factor 2 (FGF2), along with an increase in fibroblast growth factor receptor 1 (FGFR1), observed in the hippocampal tissue of patients with MDD16,18. Here, BDNF is linked to hippocampal atrophy.