Veterans with extreme mixed handedness and high combat exposure five times more likely to have PTSD

May 24 2007

A recent study conducted by investigators with the Geisinger Center for Health Research shows a clear link between combat veterans' use of both hands for common tasks and the likelihood that they will experience post-traumatic stress disorder (PTSD).

Combat veterans with an extreme level of mixed handedness are nearly twice as likely to develop (PTSD) after combat compared to veterans who use both hands less often, according to the study, which is being published in the May issue of Psychosomatic Medicine.

The study also found that veterans with extreme mixed handedness and high combat exposure were nearly five times more likely to have PTSD than those with lower degrees of mixed handedness.

Joseph Boscarino, PhD, MPH and Stuart Hoffman, DO of the Geisinger Center for Health Research measured PTSD and handedness among a national sample of 2,490 Vietnam veterans exposed to combat.

"These findings suggest the possibility of a pre-existing biological vulnerability for PTSD," said Boscarino, the study's principal investigator. "We know generally what type of soldier is likely to suffer from PTSD, before they go into combat."

While other studies on handedness and PTSD have yielded similar results, those prior studies were too small to draw significant conclusions. Boscarino's groundbreaking study examined a much larger group of patients, and therefore the results are more applicable to a large group of veterans.

"Given the research, it might be beneficial to screen people entering high-risk occupations such as the military for handedness," Boscarino said. "If pre-screening doesn't occur, the healthcare community should at least make sure that these people receive adequate post stress exposure help."

In today's context, even brief psycho-social interventions for military personnel returning from Iraq and Afghanistan could significantly reduce the risk of PTSD, said Boscarino, a Vietnam combat veteran himself.

Although therapy doesn't necessarily have to be extensive, it should occur shortly after a person has experienced a traumatic event such as combat or a natural disaster. Treatment may be critical to avoiding depression, PTSD and substance abuse related problems following such exposures, Boscarino said.

It has been theorized that people with a lesser degree of cerebral lateralization, as measured by mixed handedness, would have a greater likelihood of developing PTSD. This is because the right brain hemisphere is believed to be significant in threat identification and in the regulation of emotion responses.

People with reduced cerebral lateralization for language, as indexed by increased mixed-handedness, were thought to be more sensitive to perceived threat and prone to experience emotions more intensity. This was because their cerebral organization was thought to give primacy to right hemisphere contributions in cognitive processes.

"What we've found is a near conclusive link between handedness and a person's predisposition toward PTSD," Boscarino said. "These findings may be useful in mitigating some of the adverse outcomes associated with traumatic stressor exposures."

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