What Causes PTSD?
It may be that, when combined, the person's psychological history, the nature of the trauma, and the availability of posttrauma support cause PTSD symptoms to develop after a traumatic event. However, someone without risk factors who is exposed to a traumatic event also may develop symptoms.
Biologic Theories & PTSD
The amygdala, a structure in the brain, is part of the limbic system that is involved in the expression of emotion, especially fear, autonomic reactions (e.g., increased heart rate and blood pressure, the startle response), and emotional memory. Dysfunction in this structure may produce symptoms of PTSD.
Overwhelming trauma can cause changes in brain function that produce symptoms of PTSD: hyperarousal, numbing, sleep disturbance, irritability, intrusive emotions and memories, flashbacks, outbursts, and memory impairment.
The body responds to stress and trauma by releasing several stress hormones (e.g., norepinephrine, epinephrine). When a person is subjected to repeated or severe trauma, the physiological stress response becomes hyperactive and hyperarousal and intrusive symptoms of PTSD develop.
There also may be a biological component to numbing and other dissociative symptoms of PTSD. Some studies show that when people who have been exposed to prolonged or repeated trauma are exposed to any stimulus reminiscent of the trauma, the brain releases opiates (e.g., endorphins, enkephalins) that can produce emotional nonresponsiveness, or numbing, and amnesia.
Serotonin depletion may result from repeated exposure to severe stress and trauma, which may be a factor in the development of irritability and violent or angry outbursts in people with PTSD.