Trauma and the Brain -- long term

Research Findings Research is continuing to reveal factors that may lead to PTSD. People who have been abused as children or who have had other previous traumatic experiences are more likely to develop the disorder. In addition, it used to be believed that people who tend to be emotionally numb after a trauma were showing a healthy response; but now some researchers suspect that people who experience this emotional distancing may be more prone to PTSD. Studies in animals and humans have focused on pinpointing the specific brain areas and circuits involved in anxiety and fear, which are important for understanding anxiety disorders such as PTSD. Fear, an emotion that evolved to deal with danger, causes an automatic, rapid protective response in many systems of the body. It has been found that the fear response is coordinated by a small structure deep inside the brain, called the amygdala. The amygdala, although relatively small, is a very complicated structure, and recent research suggests that different anxiety disorders may be associated with abnormal activation of the amygdala. People with PTSD tend to have abnormal levels of key hormones involved in response to stress. When people are in danger, they produce high levels of natural opiates, which can temporarily mask pain. Scientists have found that people with PTSD continue to produce those higher levels even after the danger has passed; this may lead to the blunted emotions associated with the condition. Some studies have shown that cortisol levels are lower than normal and epinephrine and norepinephrine are higher than normal. Norepinephrine is a neurotransmitter released during stress, and one of its functions is to activate the hippocampus, the brain structure involved with organizing and storing information for long-term memory. This action of norepinephrine is thought to be one reason why people generally can remember emotionally arousing events better than other situations. Under the extreme stress of trauma, norepinephrine may act longer or more intensely on the hippocampus, leading to the formation of abnormally strong memories that are then experienced as flashbacks or intrusions. Since cortisol normally limits norepinephrine activation, low cortisol levels may represent a significant risk factor for developing PTSD. Research to understand these neurotransmitter systems involved in memories of emotionally charged events may lead to the discovery of drugs or psychosocial interventions that, if given early, could block the development of PTSD symptoms.