BDNF and psychiatric disorder: It has been observed that chronic stress elevates BDNF and increases growth of dendrites and spines in the amygdala and it was proposed that the differential effects of stress on BDNF and neural plasticity in the hippocampus and the amygdala may play role in the pathogenesis of stress-related mental disorders (Gray et al., 2013; Bennett and Lagopoulos, 2014; McEwen et al., 2016).