WASHINGTON — Roughly one in five U.S. troops is suffering from major depression or post-traumatic stress from serving in the wars in Iraq and Afghanistan, and an equal number have suffered brain injuries, a new study estimates. Only about half of them have sought treatment, says the study released Thursday by the Rand Corp. A recently completed survey showed 18.5 percent – or 300,000 people – said they have symptoms of depression or PTSD, the researchers said. Nineteen percent – or 320,000 – suffered head injuries ranging from mild concussions to penetrating head wounds. ‘There is a major health crisis facing those men and women who have served our nation in Iraq and Afghanistan,’ said Terri Tanielian, the project’s co-leader and a researcher at the nonprofit Rand. ‘Unless they receive appropriate and effective care for these mental health conditions, there will be long-term consequences for them and for the nation,’ she said in a statement. The 500-page study is the first large-scale, private assessment of its kind – including a survey of 1,965 service members across the country, from all branches of the armed forces and including those still in the military as well veterans […]