With so many soldiers suffering mild head injuries from exposure to blasts and roadside bombs, how would they cope in civilian life? Would they suffer the after-effects for years to come? And could these injuries aggravate another troubling disorder -- post-traumatic stress?

The answer appears to be no, according to a study of Minnesota National Guard troops who served in Iraq in 2006 and 2007.

Polusny, a researcher at the Minneapolis VA Health Care System, surveyed 953 Guard members during and after their deployment.

She and her colleagues discovered that the effects of mild brain injuries or concussions -- the so-called "signature injury" of the war -- probably wear off in weeks or months. When veterans have lingering symptoms, such as memory and concentration problems, that's more likely due to post-traumatic stress disorder (PTSD) than a concussion, according to the study released Monday.

The researchers did, however, find powerful evidence that combat leaves its mark in multiple ways.

A year after returning home, 42 percent of troops reported "problematic drinking." And overall, the rate of PTSD nearly doubled in that transition year, from 8 percent to 14 percent, as did depression, from 9 to 18 percent.

Surprising findings

But Polusny said she was most surprised by the concussion findings. "The thing that we struggle with as clinicians is, what is the effect on veterans if they have PTSD but also are reporting that they were exposed to a blast?" she said.

The fear, she said, was that the combination could be more devastating than PTSD alone, but the study found otherwise. Essentially, she said, the symptoms of veterans with mild head injuries were no worse than those of anyone else with post-traumatic stress.

It's believed to be the first study to show "that a history of concussion/mild traumatic brain injury alone does not contribute to long-term impairments," the authors reported. That's good news for the soldiers, Polusny said, because it means their symptoms can be treated.

"What's important is if a veteran is having difficulties in adjusting back to civilian life," she said, it's probably not because of mild head injury. "If what's driving these post-deployment problems is really PTSD, then we ought to treat the cause of it."

As part of the study, Polusny asked the soldiers to answer questionnaires while still in Iraq, shortly before they finished their 16-month tour of duty in 2007. Then she asked the same questions a year later.

Curiously, only 9 percent reported a brain injury while still serving in Iraq; a year later, 22 percent said they'd had a brain injury during combat.

"We're curious about that too," Polusny said. She speculated that some soldiers may have been reluctant to admit to injuries while still "in country," but felt freer to talk about them once they were home.

The surveys showed that concentration problems, irritability, headaches and other physical complaints were widespread among returning troops, whether or not they'd had a head injury or a PTSD diagnosis.

Higher rate of PTSD

Still, those reporting head injuries had a higher rate of post-traumatic stress than others -- about 30 percent, compared to 14 percent as a whole, she said. However, that may not be due to the injury itself, but to other factors.

Since the start of combat, thousands of troops have suffered brain injuries, most of them minor, when they were exposed to nearby blasts. As a result, the military has been screening returning troops for signs of traumatic brain injury. "However, our results suggest that screening for concussion ... does not accurately identify veterans in need of help," the authors wrote.

Polusny noted that in civilian life, most people tend to recover from concussions within a relatively short time. The study, she said, suggested that's true in combat as well. The report appears in the Archives of General Psychiatry.

Maura Lerner • 612-673-7384