Traumatic brain injury, often described as the "silent epidemic" of the Iraq war, may be less to blame for soldiers' symptoms than doctors once thought, contends a provocative military study that suggests post-traumatic stress and depression often play a role.
This is good news in a sense because there are successful treatments for those conditions, said several nonmilitary doctors who praised the research.
Still, the new findings are controversial. Brain injury experts say that it can be difficult to disentangle the lingering effects of concussion from post-traumatic stress disorder because the two conditions share many of the same symptoms.
Thousands of soldiers returning from Iraq have struggled with memory loss, irritability, trouble sleeping and other problems. Many have suffered mild blast-related concussions, but there is no easy way to tell which symptoms are due to physical damage and which are from mental problems caused by the traumatic stress of war. Imaging of the brain is being tested, but hasn't yet proven to be helpful.
The new study, based on a survey of nearly 2,500 soldiers, found that one in six solidiers returning from Iraq had suffered concussions and that brain injury made traumatic stress more likely. The study tied only one symptom — headaches — specifically to brain injury.
"The key finding in our study is that the majority of symptoms we might expect to be due to concussion are actually due to PTSD and depression," said Dr. Charles Hoge, a colonel and psychiatry chief at Walter Reed Army Institute of Research who led the study.
Hoge was to report on the survey Wednesday at a military health conference in Washington. Results also are being published in Thursday's New England Journal of Medicine.
Unraveling the symptoms
Some experts criticized the study because Hoge and his colleagues didn’t ask soldiers about some of the hallmark symptoms of brain injury or about the number of head injuries each soldier sustained.
Some of these symptoms, which can be subtle, could help distinguish the lingering effects of a brain injury from PTSD, says Wayne A. Gordon, director of the Brain Injury Research Center at the Mount Sinai School of Medicine in New York. Along with headaches, brain injury can lead to light sensitivity, trouble with organization and faulty short-term memory. After a traumatic brain injury, people often have trouble shifting from one project to another, Gordon says. And, they can have problems regulating their moods and can experience agitation.
More information might have helped researchers disentangle the effects of concussion and PTSD, says Mark Lovell, director of the sports concussion program at the University of Pittsburgh Medical Center.
It’s also possible that some of the psychiatric symptoms attributed by researchers to PTSD are actually the result of a concussion, Lovell says. “We see kids in here all the time who don’t have PTSD but who have changes in emotion and affect. Parents tell us they can’t talk to their kids anymore, that the kids can’t sleep at night. If this was a wartime setting, you might incorrectly conclude this was due to PTSD.”
Other doctors were optimistic about treatment efforts.
"It gives us hope, because we've got good treatments for PTSD," said Barbara Rothbaum, a psychologist who heads a trauma recovery program at Emory University in Atlanta. "If we can relieve the PTSD and depression, I'm hoping we'll see alleviation of a lot of these physical symptoms."
Journal editors skeptical at first
The journal's editor-in-chief, Dr. Jeffrey Drazen, said editors initially were skeptical of the findings, which depart from the gloom-and-doom picture some have painted for soldiers with brain injuries.
However, the solid research methods and the "strong and robust" data linking stress and concussion symptoms persuaded them, said Drazen, who is a scientific adviser to the Veterans Administration.
The case of Eric O'Brien, a 33-year-old Army staff sergeant from Iowa's Quad Cities, suggests the researchers may be right.
After an explosion in Baghdad in 2006, O'Brien was treated at Vanderbilt University's brain injury rehabilitation program and at Fort Campbell, Ky., for post-traumatic stress. Now he is preparing to redeploy, this time to Afghanistan.
"I retested on a lot of the tests and they showed a pretty decent increase," he said of his mental function tests. As for stress, "I don't know if it's something you just learn to deal with or if it just gets a little bit better over time," he said. "It's not as bad as it was."
The vast majority of brain injuries, or concussions, are mild, but the military previously estimated that one-fifth cause symptoms lasting a year or more.
The new study tried to pin down the potential long-term effects of mild brain injury, through an anonymous survey of two Army combat brigades — one active and one Reserve — in 2006, several months after they returned home from Iraq.
Fifteen percent of soldiers reported a mild brain injury — having been knocked unconscious or left confused or "seeing stars" after a blast, the study found. They were more likely than other soldiers to report health problems, missing work, and symptoms such as trouble concentrating.
The worst symptoms were in soldiers who lost consciousness. About 44 percent of them met the criteria for post-traumatic stress, compared with 16 percent of soldiers with non-head injuries, and only 9 percent of those with no injuries.
"The same incident might have triggered both processes," Rothbaum said, noting that after World War I, "they thought that shell shock was a neurological disorder and it turned out to have a lot of overlap with the psychological disorder."
Concussions may compound stress by damaging brain areas that tamp down responses to fear, Richard Bryant, a psychologist at the University of New South Wales in Sydney, Australia, writes in an editorial in the journal.
Soldiers who return from war with mild traumatic brain injury should be told to expect a relatively quick recovery, argues Bryant in his editorial.
"We should tell them that have sustained a knock to the head that is minor and should not cause them problems," Bryant wrote in an e-mail response to questions from msnbc.com.
That stance, he argues, could avoid creating a new post-war malady — like Gulf War Syndrome — that elicits symptoms without a cause.
This study should not be seen as a way to justify cutting federal services to returning veterans, he emphasized. "The study suggests that many troops are suffering real problems, and these are attributed to PTSD rather than mild TBI," he wrote. "This does not minimize their need for assistance in the long-term."
MSNBC.com contributor Linda Carroll, staff writer JoNel Aleccia and the Associated Press contributed to this report.