BDNF and post-traumatic stress disorder: Moreover, although previous reports have noted lower levels of BDNF from blood serum in PTSD populations (Dell’Osso et al., 2009; Berger et al., 2010; but see Hauck et al., 2009), it is unclear how this reduction relates to either a risk factor for the development of PTSD or is rather a consequence of PTSD.