Biology 202
2002 First Paper
On Serendip

After the terrorist attacks on September 11th, horrific images of the towers collapsing, survivors fleeing, and the rescue and recovery efforts inundated television viewers. In the weeks following the attacks, numerous news accounts reported increasing general anxiety among Americans, with many individuals reporting sleep difficulties and trouble concentrating. Additionally, much attention focused on the effects on those who directly witnessed and/or were injured the attacks, and whether they would suffer from post traumatic stress disorder, also known as PTSD (4). I will give a brief overview of the definition of PTSD, the neurobiology behind it, and what environmental factors may put certain people at heightened risk for developing the disorder.

Post traumatic stress-disorder is an anxiety disorder which results from exposure to an event which threatens the physical safety of an individual (1). PTSD originated as a mental illness category after the Vietnam War, when veterans exhibited sets of symptoms that did not fit into any current illness categories. However, in previous wars soldiers had complained of "shell shock" or "combat fatigue," which researchers now believe were essentially the same conditions as PTSD (2). As many as thirty percent of Vietnam veterans and eight percent of Persian Gulf War veterans exhibited symptoms of post-traumatic stress disorder (1).

Today the definition of PTSD has broadened to include not just those in combat, but people who have experienced any man-made or natural disasters, accidents, violent crime such as rape, and abuse. Symptoms may include flashbacks, nightmares, depression, anxiety, sleep problems, emotional detachment, anger, or guilt. In addition to emotional symptoms, physical symptoms such as chest pain, headaches, gastrointestinal problems, and generalized pain may occur. These symptoms must last for more than a month to be diagnosed as PTSD. Certain environmental cues that are reminiscent of the traumatic event may trigger symptoms, and anniversaries of the trauma are often difficult (1).

The biological roots of post-traumatic stress disorder also partly lie in serotonin. Serotonin is a neurotransmitter involved in such functions as hunger, aggression, sleep, and fear response. The neurons that produce serotonin have raphe nuclei in the brain stem and extend to other parts of the central nervous system, including the amygdala, a small, almond-shaped portion of the brain that controls fear response. Anxiety results in lower levels of serotonin (5), and these lower serotonin levels may act on the amygdala in some way to help produce the symptoms of post-traumatic stress disorder. The National Institute of Mental Health and the Anxiety Disorders Association of America co-sponsored a recent conference at which researchers declared that "circuits involving the central nucleus of the amygdala appear to process conditioned fear responses to specific stimuli, while circuits involving a closely related area, the bed nucleus of the stria terminalis, handle non-cue-specific, non-conditioned anxiety. Both circuits, in turn, connect to the hypothalamus , brainstem, and other brain areas mediating specific signs of fear and anxiety." However, further research on the amygdala's specific role in fear response is needed in order to understand its role in PTSD (6).

Also, traumatic events cause changes in norepinephrine and cortisol levels, which contributes to PTSD symptoms. Norepinephrine is a neurotransmitter that acts on the hippocampus, which is responsible for long-term memory storage. Norepinephrine is released in stressful situations and is present at elevated levels in individuals with PTSD. Additionally during stressful situations the hormone cortisol, which controls norepinephrine's action, is present in lower levels. As a result, in traumatic situations an elevated, less regulated level of norepinephrine acts on the hippocampus, resulting in especially vivid, long-term memories that affect PTSD sufferers (1).

Environmental factors also play an important role in the development of post-traumatic stress disorder. In the United States about 3.6 percent of 18 to 54 year-olds have PTSD (1). In the case of September 11th, approximately 70-100,000 New Yorkers were thought to be at risk of developing the disorder. Scientists believed that the number after a disaster such as the World Trade Center would be higher than for a natural disaster such as an earthquake because experiencing "deliberate violence" is generally more traumatic (4). Additionally, individuals who have previously experienced abuse or other types of trauma would be more at risk of developing PTSD after a second exposure to trauma, and women are twice as likely to develop PTSD as men (1).

Also, overall non-whites are more at risk of developing the disorder than whites. For instance, African- Americans are more likely to witness or be victims of violent crime than whites. One study found that 25 percent of African- American children who had been exposed to violence met the criteria for PTSD. Native Americans are also more likely to be exposed to violence than whites, and as a result have a PTSD rate of 22 percent. Among Asian-Americans, those who came to the United States as refugees have a particularly high chance of having post-traumatic stress disorder because of violence witnessed in their home countries and the trauma of being uprooted. For example, one-half of Cambodian adolescents who had been held in Pol Pot's concentration camps had PTSD. Similarly, Hispanic refugees from Central America have PTSD rates ranging from 33 to 60 percent (3).

The high rates among non-whites may also be worsened by a lack of access to treatment resources or a discomfort with seeking treatment from primarily white caregivers (3). However, early intervention is essential in successfully treating PTSD, since talking about the event soon after is thought to reduce the severity of symptoms. Therapists also use group therapy and exposure therapy, in which the individual gradually works through the traumatic experience again in order to confront their anxiety (1). Additionally, antidepressants such as selective serotonin reuptake inhibitors have been effective in treating PTSD, in part because individuals with PTSD often have other anxiety disorders, depression, and drug and alcohol problems that may be partly alleviated through antidepressants (1). However, further studies are needed to develop more effective medications, such as drugs that specifically target the amygdala (6).

In recent years awareness of PTSD has greatly increased as it has moved from general definitions such as "shell shock" to an official clinical condition with known symptoms and treatment. Researchers have uncovered biological bases for the disorder in the action of norepinephrine on the hippocampus and of serotonin on the amygdala. However, in treating the disorder therapists must be sensitive to the greater effect of trauma on women, and environmental factors such as the type of trauma experienced and previous exposures to traumatic events, as well as the co-occurrence of PTSD with other mental illnesses.

WWW Sources
1)National Institute of Mental Health information sheet on PTSD.

2)About.com website , On PTSD, with definitions and links to other web resources.

3) Surgeon General's Report: "Mental Health- Culture, Race, Ethnicity" . A supplement to "Mental Health: A Report of the Surgeon General 1999."

4) Scientific American . Article on September 11th and PTSD.

5) Cal State-Chico website on serotonin.

6)Anxiety Disorders Treatment Target: Amygdala Circuitry" from the ADAA 18th annual
meeting.


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