background Posttraumatic stress disorder (PTSD) is a severe anxiety disorder following exposure to a traumatic stressor with symptom clusters including reexperiencing, avoidance and hyperarousal. Neurobiological research of PTSD demonstrates changes in psychophysiology, neuroendocrinology and (functional) neuroanatomy.
aims Examination of the three following questions: (a) Is there neurobiological vulnerability for development of PTSD? (b) Which neurobiological changes arise from trauma? (c) Do neurobiological complications arise from (chronic) PTSD?
method Literature search in Medline (publications after 1989) and publications in books.
results PTSD is characterized by disregulation of the noradrenergic system, hypersensitivity of the HPA-axis, decrease of hippocampus volume, hyperperfusion of the limbic system and hypoperfusion of the prefrontal cortex. 
conclusions (a) Disregulation of the noradrenegic system and hypersensitivity of the HPA-axis are possible neurobiological vulnerabilities for development of PTSD. (b) PTSD not only shows a physiological hyperrespons and decreased cortisol, but also hyperperfusion of the limbic system and hypoperfusion of the prefrontal cortex. (c) PTSD is complicated by comorbidity of depression and alcohol abuse, which also give reduction of hippocampus volume.