This is a Newsweek article. It's an extremely depressing read.
Pvt. David Dietrich had a history of cognitive problems. He struggled in boot camp at Fort Knox, Ky., striking at least one of his superiors as unfit for the military. Dietrich was so slow at processing new things, some fellow soldiers called him Forrest Gump. His squad leader, Pfc. Matthew Berg, says Dietrich couldn't hit targets on the rifle range and had trouble retaining information. "He was very strong physically, but mentally he wasn't really all there," Berg says.
He lasted eight weeks in Iraq. Then he was shot and killed.
And this line:
He also said that in Germany, doctors had given him antidepressants and medication for attention-deficit disorder.