(CBS News) In recent years, more than 200,000 troops have tested positive for traumatic brain injuries, including concussions.
Now, CBS News correspondent Dr. Jon LaPook reports a new study finds they may be at risk for the same kind of long-term brain damage that is turning up in football players.
Nick Colgin came back from Afghanistan in 2008 with a Bronze Star for heroism and a problem that's destroying his life.
"A rocket-propelled grenade hit off the right side of my Humvee. I didn't realize it at the time but I suffered a traumatic brain injury," Colgin said. "I got home and I couldn't spell my own name and I couldn't read my own handwriting."
Four years after the explosion, his traumatic brain injury, or TBI, is all-consuming.
"The headaches have been so bad lately, that I've had to sleep in a closet just to get it dark enough so my head doesn't hurt. My depression is worse than ever," Colgin said. "All the doctors tell you that it's going to get better, the brain can heal itself, but here I am four years later and I think this is the worst moment of my experience with a TBI."
In sports like boxing and football, traumatic brain injury has been linked to a condition called chronic traumatic encephalopathy, or CTE. Symptoms include memory loss, impulse control problems, and depression.
In patients with CTE, an abnormal protein called tau damages areas responsible for thinking, judgment, emotion, and personality.
In the recent study, researchers compared the brains of athletes with known CTE with the brains of four Iraq-Afghan veterans who survived IED explosions or multiple concussions. Dr. Lee Goldstein was a lead author.
"It's quite striking and in many ways the pathology is indistinguishable to the two groups, whether you had a repeated concussion or whether you had the blast exposure, you can't really see the difference," Goldstein said.
The four veterans all developed typical symptoms of CTE and died prematurely several years later.
"A blast injury which is causing the same sort of bobbleheaded effect - only happening over milliseconds instead of seconds - is actually the same injury. It's just happening in a different situation," said neurologist Dr. Ann Mckee, a co-author of the study.
Right now, CTE can only be diagnosed after death, leaving Nick Colgin to wonder if he has it or not.
"The only thing that scares me most is that I have this and nobody will ever be able to tell me I have it until I pass away," Colgin said.
CTE increases the risk of a person slowly progressing to dementia over several decades. The hope is that by understanding what's going wrong in brain cells, researchers can develop treatments to interrupt and repair that damage.