A Pentagon official told USA Today there were concerns that Iraq veterans would blame head injuries for all manner of puzzling symptoms.

The United States did not acknowledge the mysterious Gulf War Syndrome until 1998 after more than 10,000 Gulf War vets had blamed the syndrome for causing cancer and a raft of other symptoms.

"They are reacting to rumors, things that they've read about or heard about on the Internet or (from) their friends," said Air Force Col. Kenneth Cox.

Nevertheless, scientists at the federal Defense and Veteran Brain Injury Center urged in a 2006 report that troops be screened for traumatic brain injuries (TBI) immediately.

The military will soon begin testing all returning troops for TBI, Cox said.