|A new clinical tool for assessing post-traumatic stress disorder (PTSD), developed by the Atlanta Center for Behavioral Neuroscience (CBN), the Atlanta Veterans Affairs Medical Center (VAMC), and Emory University School of Medicine, could enable researchers to develop better treatments for war veterans suffering from the disabling anxiety disorder. Pilot studies of the system are currently being conducted with Vietnam War veterans at the Atlanta VA, and will soon be launched with Iraq War veterans at Fort Bragg, NC, and Serbo-Croatian War veterans in Zagreb, Croatia.
PTSD, which affects an estimated 20 percent of veterans in recent conflicts, is a dysfunction of the brain's fear control mechanisms resulting from a psychologically traumatic experience, such as combat. One of the central features of the disorder is the inability of the brain to distinguish between dangerous and safe situations.
"The sound of a helicopter flying overhead can be enough to trigger anxiety or panic attacks in vets with PTSD," said Tanja Jovanovic, PhD, an Emory and CBN post-doctoral fellow in the laboratory of Erica Duncan, MD, of the Atlanta VAMC, CBN and the Department of Psychiatry and Behavioral Sciences at Emory University School of Medicine. "They know that they are not back in combat, but they can't suppress their fear."
The new PTSD testing system determines the extent of the impairment in the brain's fear control mechanisms. A patient is initially conditioned to fear a series of lights by pairing their appearance with an aversive air blast to the throat. A second set of safety lights are then presented without an air blast. Finally, the two sets of lights are displayed together without an air blast to test the patient's ability to inhibit their fear of the lights. Electrodes attached under the eye measure fear responses based on blink size during each of the three tests. Larger blinks indicate a greater fear reaction.
In a preliminary study of Vietnam War veterans, Jovanovic and her colleagues determined PTSD sufferers were more afraid of the lights than control subjects. Veterans with more severe PTSD symptoms also could not inhibit their fear when presented with both sets of lights, indicative of the dysfunction in their fear control mechanisms.
Clinicians typically assess PTSD sufferers based on subjective accounts of their symptoms. "This new system will provide a new way to objectively test their fear control mechanisms," said Jovanovic, "Our hope is that it will lead to the development of effective treatments for relieving fear in PTSD sufferers and others with anxiety-related disorders."
The researchers' next step is to determine whether specific genes are involved in fear inhibition. Other studies are using functional magnetic resonance imaging to examine brain activation patterns involved in fear inhibition.
Development of the human PTSD testing system was based on animal research conducted by Karyn Myers, PhD, and Michael Davis, PhD, of Emory University and CBN. Additional researchers at the Atlanta VAMC and Emory involved in the human studies include Seth Norrholm, PhD, Megan Keyes, PhD, and Ana Fiallos, BSEE. The research was supported by grants from CBN and an American Psychiatric Association/Glaxo SmithKline Award to Dr. Duncan, a National Institute of Mental Health (NIMH) grant to Barbara Rothbaum, PhD, of the Department of Psychiatry and Behavioral Sciences at Emory University School of Medicine, and a Kirchstein Individual Postdoctoral Fellowship from NIMH to Dr. Jovanovic.