Up to one in five soldiers returning from combat in Iraq and Afghanistan has a mild brain injury.
Brain injuries, the most common of which is a concussion, occur when a powerful blast shakes the brain inside the skull.
The report showed as many as 20 percent of soldiers have had a concussion, but many don't recognize the symptoms and it goes unreported. Symptoms include headaches, dizziness, irritability and sleep disorders.
The army is now screening every returning soldier for the injuries.
The report also showed six percent of soldiers show signs of severe traumatic brain injuries, and 5 percent have penetrating head wounds. The study was part of the Army's task force report.