BDNF and major depressive disorder: Patients with depression generally present neurodegeneration and smaller hippocampal and prefrontal cortex volume (Brown et al., 2018; Iimori et al., 2018; Roody et al., 2018) and such reductions are not only due to neuronal death, but also caused by decreased neuroplasticity and neurogenesis secondary reduced expression of neurotrophic factors, such as BDNF (Kraus et al., 2017; Jesulola et al., 2018).