A study conducted on identical male twins has revealed that Vietnam war veterans with post-traumatic stress disorder (PTSD) and their non-combat exposed, identical twins portrayed slight neurologic deficits that veterans without PTSD and their twins did not have, suggesting that the existence of deficits may actually predispose individuals to PTSD, according to an article in the May issue of Archives of General Psychiatry, one of the JAMA/Archives journals.
PTSD is an anxiety disorder that develops after exposure to combat or another extremely disturbing event. Previous studies have found diminished volume of certain brain structures among individuals with PTSD, according to background information in the article. Researchers have proposed that the traumatic events experienced by these patients or the PTSD itself caused the damage. However, others hypothesize that some brain abnormalities may precede exposure to a traumatic event and increase the risk that a person who experiences such an event would develop PTSD.
Tamara V. Gurvits, M.D., Ph.D., Veterans Affairs Medical Center, Manchester, N.H., and colleagues studied 49 male Vietnam veterans and their identical twins, who had not experienced combat. Among the veterans, 25 had PTSD and 24 had never had PTSD. All of the participants were evaluated by a neurologist-psychiatrist, who gave them a score of zero to three on each of 45 neurologic tests, such as copying drawings of figures. A higher score indicated the presence of a subtle neurologic finding associated with difficulties in behavior, coordination and learning.
Veterans with PTSD had higher scores than veterans without PTSD, indicating the presence of more minor neurologic abnormalities. The non-combat exposed twins of the combat veterans who had developed PTSD also had significantly higher scores than the non-combat exposed twins of the combat veterans who did not have the disorder. The results remained significant even when the researchers adjusted for factors such as age, the number of traumatic events experienced that were not related to combat, alcoholism or anxiety disorders.
The higher scores among PTSD veterans and their twins suggest a dysfunction in the cerebral cortex, the authors write. This part of the brain is necessary in reducing the fear response that occurs after a traumatic event. Therefore, this type of dysfunction could either increase the risk of developing PTSD after such an event or reduce the likelihood that individuals who do develop the condition will recover, increasing the likelihood of chronic cases. "It is also possible to phrase these relationships inversely," the authors write. "That is, a healthy nervous system may, for all the previously mentioned reasons, confer resilience in the face of highly stressful life events."