BDNF and post-traumatic stress disorder: 2006). BDNF has a role in activity‐dependent neural plasticity processes of the hippocampus and amygdala, implicated in long‐term learning and memory (Hariri et al. 2003; Andero and Ressler 2012; Mahan and Ressler 2012). In one study, low BDNF serum levels were associated with PTSD, while another reported no relationship to PTSD in victims of urban violence (Valente et al. 2011). However, the Met allele (one and two alleles) of BDNF Val66Met polymorphism may be associated with PTSD severity in veterans (Pivac et al. 2012).