Injury to specific brain regions may reduce PTSD risk
Military veterans wounded in certain brain regions during combat were less likely to later develop post-traumatic stress disorder (PTSD) than those injured in other areas of the brain, according to a new study. The findings suggest new strategies for potential PTSD therapies that use drugs or other interventions to dampen activity in these brain regions.
PTSD is a chronic anxiety disorder that affects millions of Americans. People with PTSD persistently relive a traumatic experience through nightmares and flashbacks that may seem real. They may become emotionally numb, or they may startle easily and be constantly on guard. About 20-30 percent of Vietnam War veterans have been diagnosed with PTSD, and a similar rate has been reported among survivors of Hurricane Katrina in New Orleans. Other traumatic events—including assault, rape, child abuse or traffic accidents—can also trigger PTSD.
Previous studies have shown that PTSD is associated with changes in brain activity. However, those earlier investigations could not determine whether the brain changes were contributing to or arising from the disorder. In the new study, a research team including scientists from NIH's National Institute of Neurological Disorders and Stroke (NINDS) and the National Naval Medical Center set out to make that distinction. Their results were published Dec. 23, 2007, in the online edition of Nature Neuroscience.
The scientists analyzed brain scans from 193 Vietnam War veterans who had sustained penetrating head injuries during combat. For comparison, they looked at another 52 veterans who been in combat but had no head injuries. Psychological tests conducted from 2003-2006 showed that about one-third of the 245 participants had developed PTSD at some point in their lives. The scientists then compared the distribution of injuries in various brain regions between those who had developed PTSD and those who had not.
The researchers found that PTSD rarely occurred in veterans who had damage to either of 2 brain regions—the amygdala or the ventromedial prefrontal cortex (vmPFC). The amygdala plays a role in fear and anxiety, and the vmPFC is involved in higher mental functions and planning. Among veterans with injury to other brain regions or no brain injury at all, at least 40 percent had developed PTSD. In contrast, only 18 percent of those with damage to vmPFC and none of the 15 veterans with damage to the amygdala developed PTSD.
Although the study was limited to male veterans, the scientists believe that their findings may be broadly applicable to other populations and other types of trauma. Previous studies in other populations have linked PTSD to alterations in the amygdala and the vmPFC. The researchers suggest that future treatments for PTSD might seek to reduce brain activity in these two brain regions, perhaps through drugs or pacemaker-like devices.
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