A new study has suggested that some brain injuries reduce the likelihood of developing post-traumatic stress disorder, leading to the possibility that dampening activity in these brain regions may be effective treatments for PTSD.
Lead researcher Dr. Jordan Grafman, a senior investigator at the National Institute of Neurological Disorders and Stroke (NINDS), revealed that his team's findings are based on a study of the brains of Vietnam War veterans.
Posttraumatic Stress Disorder (PTSD) is an anxiety disorder that can develop after exposure to a terrifying event or ordeal in which grave physical harm occurred or was threatened. It is a severe and ongoing emotional reaction to an extreme psychological trauma.
PTSD involves the persistent reliving of a traumatic experience through nightmares and flashbacks that may seem real.
During the study, the researchers reviewed Vietnam veterans who had sustained penetrating brain injuries, and found that they were less likely to develop PTSD.
The findings suggest that drugs or pacemaker-like devices aimed at dampening activity in these brain regions may be effective treatments for PTSD.
"If we could show that lesions in a specific brain region eliminated PTSD, we knew we could say that the region is critical to developing the disorder," Nature Neuroscience quoted Dr. Grafman as saying.
In all, 193 veterans with sustained penetrating brain injuries and 52 veterans with combat exposure, but no head injury, were reviewed.
Using CT (Computerized Tomography) scans to map the participants' brain injuries, the researchers classified them as either having developed PTSD at some point in their lifetime or having never developed PTSD.
A comparison of the distribution of brain injuries between the two groups revealed two brain regions where damage was rarely associated with PTSD, namely, the amygdala and the ventromedial prefrontal cortex (vmPFC).
While the amygdala is a structure important in fear and anxiety, the vmPFC is an area involved in higher mental functions and planning.
In another level of analysis, the researchers compared the prevalence of PTSD in subjects with damage to either the amygdala or vmPFC, subjects with damage to other parts of the brain, and subjects without any head injury.
The researchers found that PTSD occurred in a similar fraction of subjects in the last two groups—40 percent and 48 percent, respectively.
By contrast, PTSD occurred in only 18 percent of subjects with damage to the vmPFC. Subjects with damage to the amygdala did not suffer it.
The occurrence of other anxiety disorders was not affected by damage to the amygdala or vmPFC.
"It appears that if you have damage to either of those areas, you're not likely to develop PTSD," said Grafman.
The researchers believe that drugs designed to inhibit the activity of the two structures might provide relief from PTSD.
Deep brain stimulation, a technique used to treat Parkinson's disease by modifying the brain's electrical activity, might also prove useful against PTSD if targeted to the amygdala or vmPFC, they say.