Knocked unconscious when a roadside bomb sent his armored vehicle flying in Iraq, US Army Lieutenant Mike McMichael's life has been haunted ever since by invisible wounds that never seem to heal.

With an impaired memory and intense anxiety, McMichael suffers from what top generals call the signature wounds of the Iraq war, traumatic brain injury (TBI) and post-traumatic stress disorder (PTSD).

Even as President Barack Obama prepares to declare an end to the combat mission in Iraq, veterans like McMichael are waging another war at home against the debilitating effects of concussions and combat stress.

The wounds plague hundreds of thousands of soldiers and veterans, exacting an emotional cost on families and a growing financial burden for the US government and society.

The military and veterans' agencies have struggled to cope with the condition that often leaves soldiers a shadow of their former selves, unable to keep a job or perform basic tasks.

McMichael looked healthy when he arrived back in Raleigh, North Carolina in January 2005, only about two weeks after the explosion that knocked him out for several minutes. But his wife soon realized her husband had changed dramatically.

"Before Iraq, he was the life of the party, he would have no problems talking to anybody. He thrived on life's stresses," his wife Jackie told AFP.

"He came back and I don't know how to describe it, he was a little different."

He was detached from his children, given to angry outbursts and tormented by hallucinations. There were symptoms too of something beyond the purely psychological.

The former National Guard soldier got lost on familiar roads, had frequent migraines and had trouble reading or figuring out when to brake for a stop sign.

"It's very bewildering," he said. "A lot of times I won't remember exactly where I am."

Retired from the National Guard, McMichael, 36, sought help from civilian psychiatrists, who were unfamiliar with the stresses faced by combat veterans and prescribed an array of drugs that left him groggy and withdrawn.

McMichael's life began to unravel. He trashed his house in a violent outburst, and had to be placed in a mental hospital. He was fired from his job at a company where he had once excelled and briefly left his wife.

"We miss the old Mike," his colleagues told him.

"That was so disheartening," McMichael said. "I couldn't find him. The old Mike wasn't there."

Going out to a restaurant filled him with dread, and for a long time he refused. "The noise, the movement. You're always looking for the bad guy in the crowd. You couldn't shut off your combat mode," McMichael added.

He applied for disability benefits, but encountered a baffling labyrinth of government bureaucracy. All the while, his brain injury went undiagnosed.

It was not until his wife testified before a Senate committee in March 2008, that his paperwork was finally approved and the Department of Veterans Affairs (VA) formally recognized his TBI.

The Pentagon has scrambled to address the problem, hiring hundreds of mental health professionals, sending counselors out to warzones and trying to learn from emerging science on brain injuries.

Top brass have also spoken out in a drive to change attitudes in the military about mental health, telling troops that seeking counseling will not damage their careers and urging commanders to help troubled soldiers.

McMichael's care improved in the last two years, and he said the VA has learned how to better treat traumatic brain injuries. The military has introduced rules that require soldiers to be taken off duty and examined if they suffer concussions near blasts.

McMichael, who has no regrets about his military service or the US invasion of Iraq, has shown signs of progress. He said he's now engaged with his three children, his tremors have receded and he ventures out of the house more often.

He volunteers at his kids' school and with veterans' groups, but he is still unable to handle the stresses or the skills required for a full-time job. He said he feels guilty about receiving disability pay.

In case he forgets the way home from errands or how to get to his mother's house, McMichael has a GPS in his car, and his household chores are punched into his phone as a reminder.

He identifies with other veterans whose wounds are not visible, and who sometimes feel misunderstood and cut off from the rest of a society that has been virtually untouched by the war.

"What you'll hear a lot of them say is, 'I almost wish I had a more severe injury that's more visible, like I was missing an arm or leg,' because people will see right away that you went through something horrible."