The Biology Of PTSD
To understand the biology of PTSD, one must note the difference between a response to stress and a response to life-threatening trauma. Exposure to stress results in negative health outcomes, including psychiatric symptoms. Stress can be relieved, with the body no longer reacting to it. With PTSD, adverse effects associated with exposure to trauma continue even decades after the traumatic event.
The response to fear is centered in the brain's amygdala, the major interface between experience and the body's biochemical response to it. The amygdala decides whether there should be a stress response and, if so, begins the process of activating the neurochemical and neuroanatomical circuitry of fear.
It can be just milliseconds before the startle reflex and other defense mechanisms are activated in the central nervous system. The heart rate skyrockets, muscles become flooded with glucose and the "fight-or-flight" response takes over. The hormones cortisol and catecholamines also are released, and the higher the stress level, the greater the cortisol dump. Catecholamines help deliver energy; cortisol works to eventually shut down the emergency response.
With PTSD, cortisol levels are lowered rather than increased as they are in a classic stress response. Researchers are focusing on how and why trauma can lead to changes in the brain that can produce PTSD symptoms in some individuals but not in others.
The question is...why has there been a failure of the body to return to its pretraumatic state?"
The biology of PTSD seems, in many respects, to be different than biological alterations observed in other psychiatric disorders.
Researchers once thought that low cortisol levels indicated that PTSD sufferers had developed a long-term adaptation to stress. But research has shown that they have reduced volume in the brain's hippocampus, which may be damaged by a massive overdose of cortisol. Many symptoms of PTSD and depression are similar, but PTSD creates different physical changes than depression.
No cure has been found to date.
