Review article
Neurobiology of posttraumatic stress disorder

Stress is a set of biological reactions in the body. These reactions start when the body is exposed to the negative factor of a stressor, which can have different levels of intensity. After a personal experience or by witnessing a traumatic event, a strong stress response is formed in the body. That may cause the development of the post-traumatic stress disorder (PTSD). Post-traumatic stress disorder is classified as a separate disease entity, and has been introduced into the Diagnostic and Statistical Manual (DSM) in the United States. This syndrome is usually diagnosed in veterans, victims and witnesses of traffic accidents, or natural disasters. The characteristic symptoms are: returning to the trauma in memories (flashbacks), nightmares, poor concentration, and isolation from society. Post-traumatic stress disorder causes significant biochemical changes in brain tissue. This leads to disturbances in the functioning of monoaminergic systems: the noradrenergic, dopaminergic, serotonergic and limbic systems. Furthermore, prolonged stress can lead to changes in the body. Disturbances linked with neurotransmitter levels may last long after the event that triggered the fear. After the traumatic events, higher levels of hormones which are produced during the stress situation can be a vital factor toward the development of PTSD. The prolonged effect of an intensive stressor causes, at first, activation of the sympathetic–adrenomedullary system and then activation of the hypothalamic–pituitary–adrenal (HPA) axis.