BDNF and post-traumatic stress disorder: Whilst this has provided insight into many areas of the neurobiological system and various “symptoms” associated with PTSD, Hemmings et al. (2013b) recently stated that “no gene variant has yet been reported as unequivocally involved in the development of this disorder [PTSD].” We suggest that the Brain Derived Neurotropic Factor (BDNF) gene may be that gene: primarily because of its role in hippocampal processing and its recent associations with PTSD.