The disorder is most commonly seen in combat veterans. It is characterized as surviving a "traumatic experience," such as a terrorist bomb blast, combat, a violent physical attack or a severe car accident.
"A trauma is defined as an unexpected abnormal event and Sept. 11 certainly qualifies," Joseph Ledoux, a researcher at New York University, told United Press International. "It's the normal fear process that activates the 'fight or flight' reaction, but when it becomes prolonged -- more than one month -- it's considered post traumatic stress disorder."
People who suffer from the disorder re-experience the trauma in nightmares or intrusive thoughts. They avoid reminders or the trauma location. Many become emotionally numb or show hypersensitivity to other events by doing things like getting startled easily.
"During a stressful event, the brain experiences heightened memory," Ledoux said. "For example, people remember exactly what they were doing when they heard Kennedy got shot."
But the more severe the trauma, the more cognitive function is impaired, Ledoux said. Too many hormones are being pumped around the body and the hippocampus -- the part of the brain that deals with memory -- is vulnerable. Some cells die. Under severe trauma, parts of the hippocampus can shrink, Ledoux said.
For example, there have been several studies on rats learning a route by swimming or walking through a maze. However, put a cat inside the room with the rat and the rat forgets the route and can't make it through the maze.
"Rats are scared of cats, even rats whose parents have been bred in a lab and never seen a cat, will experience fear and the biochemical reaction to fear when a cat is nearby," Ledoux said. "People experiencing memory loss or the ability to concentrate after Sept. 11 would not be unusual."
The Center for the Neuroscience of Fear and Anxiety, a National Institute of Mental Health-/NIH-sponsored research program of basic science and clinical research about the brain mechanisms of anger and anxiety, is examining how long-term stress alters the brain and thereby the way people think, feel and behave at work and in their personal lives.
The center, directed by Ledoux, is based at New York University. Scientists at New York University, Rockefeller University, Cornell University, Columbia University and Mount Sinai Hospital also collaborate.
"With the advent of MRI and new technologies to examine the brain by non-invasive ways we've made substantial progress in the last decade in understanding how some parts of the brain function," said David Silbersweig, a doctor at Weill Cornell Medical College at Cornell University.
The disorder usually lasts about six to 12 months, but it depends on the severity of trauma, how long a person is exposed to the trauma and his emotional, psychological and social history.
"If a person has a history of being able to deal well with change and stress, they may deal with it better, but there's no way of telling who will get post traumatic stress disorder. A person who has an earlier history of a mental condition such as depression may be more susceptible," R. Andrew Harper, a psychologist at the University of Texas in Houston, told UPI.
However, some may have the disorder chronically. Some may function immediately after the trauma and not examine their feelings for years. Many combat veterans go through the disorder 20 years or more after combat.
Studies show that about 14 percent or even up to 23 percent of people who experience a traumatic event will get the disorder. If two people experience the same trauma one may develop post traumatic stress disorder and one may not.
"Therapy can help, but people have to ask for it and be a willing participant," Harper said. "It's not enough for the fire department to order its members for counseling if some don't want to be there -- some may recover on their own."
Since Sept. 11, 25 percent of American adults say they have increased, resumed or started smoking cigarettes, taken up bad eating habits or started drinking more caffeine or alcohol, according to the American Cancer Society. The American Dietetic Association noted snack food sales have risen 15 percent.
"People temporarily seeking refuge in potato chips or some beers should not be concerned because it may be a way for some to cope," Harper said. "But what you want to watch out for is it escalating and then becoming an unhealthy habit."
Treatment that includes pharmaceuticals and counseling is recommended. Drug therapy using anti-depressants such as Prozac or Zoloft, reduces anxiety symptoms.
"Counseling is helpful because it allows a person not only to explain what happened and why it's so upsetting but it allows the therapist to put it in a larger context," Marylene Cloitre, a researcher at Weill Cornell Medical College at Cornell University, told UPI. "If someone says, 'I can't believe people are so evil,' the therapist can point out that 'Yes, there are evil people but there are equally wonderful caring people'."
(Reported by Alex Cukan in Albany, N.Y.)