Although the effects of acute stress are usually brief and can be overcome quickly, exposure to chronic or extreme forms of un-escapable stress can lead to neurochemical, morphological and functional changes in the brain that have been associated with posttraumatic stress disorder (PTSD) and major depressive disorder (MDD). These stress-induced psychiatric diseases are characterized by symptoms such as intrusive distressing thoughts, anhedonia, and irritability feelings of guilt, sleep disorders, cognitive impairment, anxiety and sometimes treatment-resistant depression. Furthermore, these conditions have been associated with functional and structural changes in several regions of the brain including the amygdala, entorhinal cortex, prefrontal cortex and hippocampus. At cellular level, PTSD and depression are also associated with a decrease of glial fibrillary acidic protein (GFAP) immunoreactive cells (GFAP+) in the brain. GFAP is a family of proteins that includes eight isoforms expressed by different subpopulations of astrocytes as well as immature brain cells. These isoform include GFAP+ 1, GFAP delta and GFAP kappa.