Post-Traumatic Stress Disorder (Causes)

Although it is always kicked off by a terrifying event, PTSD may have roots in biology as much as in experience. Exposure therapy and other psychotherapy, and medication, all have a role in treating the flashbacks, anger outbursts, physical distress and other signs of the disorder.

People who have suffered childhood abuse or other previous traumatic experiences are more likely to develop the disorder. And people who experience emotional distancing may be more prone to PTSD.

Studies in animals and humans have pinpointed the brain areas 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 the body. The fear response is coordinated by a small structure deep inside the brain, called the amygdala. The amygdala, is a complicated structure, and research suggests that posttraumatic stress disorder may be associated with abnormal activation of the amygdala.

Once fear is conditioned in the amygdala, it is hard to change. However, the neural pathways from the amygdala to the hippocampus and to cortical regions such as the frontal lobes allow its suppression until triggered. Fear quickly returns when the individual is re-exposed. An increase in stressors seems to affect the fear-inducing and the fear-inhibiting pathways. High stress levels decrease the capacity to suppress fear, while increasing the ability to induce it. Thus, the fear induced by re-exposure to traumatic material indicates a failure of inhibition on the part of the hippocampus, and is evidence that the traumatic episode is not integrated as a narrative, spatio-temporal event in autobiographical memory. Furthermore, the heightened sensitivity of exposure of PTSD patients to trauma-related material results in an increase in fearfulness in response to stimuli that are not truly life threatening.

Studies using MRI in PTSD have measured volume of the hippocampus, a brain structure involved in learning and memory. Patients with combat-related PTSD had an 8 percent decrease in right hippocampal volume when compared with controls. A decrease of 12 percent in left hippocampal volume was found in patients with a history of PTSD related to severe childhood physical and sexual abuse. Reduced hippocampal volume was associated with dissociative symptoms in women who had a history of childhood sexual abuse.

People with PTSD tend to have abnormally high levels of key hormones involved in response to stress. A person in danger produces 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, which might 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 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.

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