This hippocampal atrophy is posited to be the result of chronic stress exposure leading to sustained decreases in neuroprotective factors [e.g., brain-derived neurotrophic factor (BDNF) expression and signaling] that damage or hinder plasticity, fostering neuronal atrophy and decreased synaptic number and function, particularly in medial PFC and hippocampus [21, 22]. Here, BDNF is linked to hippocampal atrophy.