The Pentagon has decided that it will not award the Purple Heart, the hallowed medal given to those wounded or killed by enemy action, to war veterans who suffer from post-traumatic stress disorder because it is not a physical wound.

The decision ends the hope of Iraq and Afghanistan veterans who have the condition and had hoped that the Purple Hearts could honor their sacrifice and help remove some of the stigma associated with the condition.

The disorder, which may go unrecognized for months or years, can include recurring nightmares, uncontrolled rage and, sometimes, severe depression and suicide. Soldiers grappling with PTSD are often unable to hold down jobs.

In May, Defense Secretary Robert Gates said awarding Purple Hearts to such service members was “clearly something that needs to be looked at,” after he toured a mental health center at Fort Bliss, Texas.

But a Pentagon advisory group decided against the award because, it said, the condition had not been intentionally caused by enemy action, like a bomb or bullet, and because it remained difficult to diagnose and quantify.

“Historically, the Purple Heart has never been awarded for mental disorders or psychological conditions resulting from witnessing or experiencing traumatic combat events,” Eileen Lainez, a Pentagon spokeswoman, said in a statement on Tuesday.

One in five service members, or at least 300,000, suffer from post-traumatic stress disorder or major depression, according to a Rand Corp. study in 2008.