[Biological basis of posttraumatic stress disorder].

Neuroendocrinological research on the physiological systems involved in stress evidenced hyper functioning of the sympatho-adrenal axis together with reduced activity of the hypothalamic-pituitary-adrenal axis in patients with posttraumatic stress disorder (PTSD). An impaired corticoid response to stressors seems to be associated with enhanced vulnerability to PTSD. Excess catecholamines, unchecked by corticoids would promote over consolidation of traumatic memories and undue generalization to other stressful situations. Symptoms such as numbing and flashbacks have been related to endogenous opioids. Neuroimaging studies evidenced a reduction of hippocampal volume in PTSD patients, which has been related to both cognitive changes and abnormalities of the HPA axis that are found in PTSD.