The Biology of PTSD

From: Tommy Dorris <tommyded@pacifier.com>

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The Biology of PTSD

Jun 1, 2001
Randy Fillmore
Stars and Stripes Medical Correspondent

To understand the biology of PTSD, one must differentiate the body's
response to stress from its response to life-threatening trauma, says Rachel
Yehuda, Ph.D., of the Bronx VAMC psychiatry department and Mount Sinai
Medical Center in New York.

"Exposure to stress results in a myriad of negative health outcomes,
including psychiatric symptoms," says Yehuda. Stress can be relieved, with
the body no longer reacting to it. "However, with PTSD, adverse effects
associated with exposure to trauma continue even decades after the traumatic
event."

The body's response to fear is centered in the brain's amygdala, the major
interface between experience and the body's biochemical response to it.

The amygdala decides whether there should be a stress response and, if so,
begins the process of activating the neurochemical and neuroanatomical
circuitry of fear.
- Dr. Rachel Yehuda

"The amygdala decides whether there should be a stress response and, if so,
begins the process of activating the neurochemical and neuroanatomical
circuitry of fear," explains Yehuda.

It can be just milliseconds before the startle reflex and other defense
mechanisms are activated in the central nervous system. The heart rate
skyrockets, muscles become flooded with glucose and the "fight-or-flight"
response takes over. The hormones cortisol and catecholamines also are
released, and the higher the stress level, the greater the cortisol dump.
Catecholamines help deliver energy; cortisol works to eventually shut down
the emergency response.

With PTSD, says Yehuda, cortisol levels are lowered rather than increased as
they are in a classic stress response. Researchers are focusing on how and
why trauma can lead to changes in the brain that can produce PTSD symptoms
in some individuals but not in others.

The essential question, says Yehuda, is: "Why has there been a failure of
the body to return to its pretraumatic state?"

The biology of PTSD seems, in many respects, to be different than biological
alterations observed in other psychiatric disorders.
- Dr. Rachel Yehuda

Researchers once thought that low cortisol levels indicated that PTSD
sufferers had developed a long-term adaptation to stress. But research has
shown that they have reduced volume in the brain's hippocampus, which may be
damaged by a massive overdose of cortisol.

"The biology of PTSD seems, in many respects, to be different than
biological alterations observed in other psychiatric disorders, particularly
major depressive disorder," observes Yehuda, yet many symptoms of PTSD and
depression are similar.

"As our understanding grows, we will be able to understand mechanisms of
actions of various treatments. Even more promising, however, is the
opportunity to develop treatments that are geared specifically toward
restoring biological systems."