[ABSTRACT] Post-traumatic stress disorder (PTSD) is a chronic and disabling disorder for which current treatments are only partially effective. A greater knowledge of the psychobiological background of this disorder is necessary in order to be able to allow patients to live in the present with freedom from feelings or behaviours that belong to the past. The biological bases of PTSD could represent the long term consequences of a failure of the organism to recover from a traumatic event, or the b