BDNF and depressive disorder: Studies have shown that the volume of the hippocampus and prefrontal cortex (PFC) is reduced in patients with depression [1-2]. Reduced levels of BDNF were found in the hippocampus and prefrontal cortex in rodent models after exposure to different types of stress [3-5]. Post-mortem analyses also reveal reduced BDNF levels in these areas in the brains of patients with depression [3].