BDNF and post-traumatic stress disorder: Peripheral BDFN levels are lower in psychiatric disorders (Boulle et al., 2012), and a recent systematic review has shown that BDNF seems to present variations after psychotherapy, especially in patients with bulimia, post-traumatic stress disorder (PTSD), insomnia, and borderline personality disorder, with a reduction in symptomatology (Claudino et al., 2020).