Post-traumatic stress disorder, a mental health condition triggered by witnessing or living through a traumatic event, is linked to a host of emotional side effects, including anxiety, flashbacks and nightmares. Now, new research indicates PTSD might physically change the brain, too.

Researchers at University of California San Diego Health took brain scans of 89 former or current military members with mild traumatic brain injuries, and used a symptom scale to identify 29 of those individuals as having significant PTSD. After measuring the participants' brains, the researchers found individuals with PTSD had a larger amygdala, which is the region of the brain associated with controlling emotions, including fear.

"It could be that individuals prone to PTSD symptoms after a head injury have a larger amygdala to begin with, that they have a brain primed to respond to fear and startle reflexes in an exaggerated fashion," Dr. Douglas Chang, study author, professor and chief of physical medicine and rehabilitation service at UC San Diego Health, told HuffPost.

"Or these results could be the result of neuroplasticity, of a brain reaction to fear conditions resulting in growth of the neural networks of the amygdala fear processing organ."

(The study, which will be presented at the American Academy of Neurology's Sports Concussion Conference July 14 to 16, has not yet been published in a peer-reviewed journal.)

The study was limited to military members who suffered blast injuries, so it's not clear whether the findings would translate to a more general population, such as individuals who've experienced sports-related concussions.

Still, if the findings are sufficiently replicated, the researchers hope they could be a useful tool for PTSD screening and treatment.
"We wonder if amygdala size could be used to screen who is most at risk to develop PTSD symptoms after [a traumatic brain injury]," Chang said.

"On the other hand, if there are environmental or psychological cues that lead to neuroplasticity and enlargement of the amygdala, then maybe such influences can be followed and treated."
As it stands, nearly 8 million Americans will experience PTSD in a given year, and 8 percent of the population will have PTSD at some point during their lifetime, according to the U.S. Department of Veterans Affairs.