Despite vigorous lobbying by some combat veterans and U.S. military psychologists and medical officials, the U.S. Department of Defense turned down a proposal to award troops who get PTSD (post-traumatic stress disorder) the Purple Heart medal. The Purple Heart is an award for physical wounds, and replaced earlier recognition (in the form of wound badges and such) in the 1930s.
The army has, over the years, developed a set of guidelines for how to recognize the symptoms of combat fatigue (or PTSD). With all the attention PTSD has gotten in the media of late, troops are more willing to seek treatment. But while extreme cases of PTSD are pretty obvious, but it's the more subtle ones that army wants to catch early. These are easier to cure if treated promptly. Some of the proponents for PTSD Purple Hearts believed that the award of these medals would make it easier for PTSD sufferers to seek treatment early on.
The problem with giving a medal for PTSD is that, again, except in severe cases, it's not certain who has it. A physical wound is pretty unambiguous. Even some mental injuries, like a concussion, can be proven via an x-ray image. And this is where PTSD is going. Brain activity imaging (mainly via MRI) is a rapidly growing field, and some types of PTSD can be identified this way. But it's got a way to go, perhaps 5-10 years, before you can put someone in an MRI (or whatever) scanner and determine if they have PTSD. That still leaves open the question of what caused the PTSD. We all suffer from PTSD to a certain extent. Accidents, a death in the family or other traumatic events can do it. But eventually, a PTSD "wound" will be as easy, well, almost as easy, to identify as a bullet wound. Then they may start handing out Purple Hearts for what was called, after the American Civil War (1861-65), "Irritable Heart," in World War I "shell shock" and in World War II "combat fatigue."