Via NPR's Shots blog: Concussions May Increase The Risk Of PTSD. Excerpt:
There's growing evidence that a physical injury to the brain can make people susceptible to post-traumatic stress disorder.
Studies of troops who deployed to Iraq and Afghanistan have found that service members who have suffered a concussion or mild traumatic brain injury are far more likely to develop PTSD, a condition that can cause flashbacks, nightmares and severe anxiety for years after a traumatic event.
And research on both people and animals suggests the reason is that a brain injury can disrupt circuits that normally dampen the response to a frightening event. The result is like "driving a car and the brake's not fully functioning," says Mingxiong Huang, a biomedical physicist at the University of California, San Diego.
Scientists have suspected a link between traumatic brain injury (TBI) and PTSD for many years. But the evidence was murky until researchers began studying troops returning from Iraq and Afghanistan.
What they found was a lot of service members like Charles Mayer, an Army sniper from San Diego who developed PTSD after finishing a deployment in Iraq.
In 2010, Mayer was on patrol in an Army Humvee near Baghdad when a roadside bomb went off. "I was unconscious for several minutes," he says. So he found out what happened from the people who dragged him out.
The blast fractured Mayer's spine. It also affected his memory and thinking. That became painfully clear when Mayer got out of the Army in 2012.
"Two weeks later, I started school," he says. "And a simple math equation like 120 times 7, where I previously would do that in my head very easily, I all of a sudden couldn't do that."
And Mayer had a bigger problem. His time in Iraq had left him with an uncontrollable fear of improvised explosive devices, or IEDs.
"When I would walk down the street, I would walk away from trash piles because that's often how they would hide IEDs," he says. "I stayed away from large crowds."