Over time, the medical and military labels for this condition have evolved to sound more sterile, moving from the visceral "shell shock" of WWI to "battle fatigue" in WWII, "operational exhaustion" in Korea, and finally Post-Traumatic Stress Disorder (PTSD) today. The Psychology: Why the Brain Disconnects
It is also sometimes observed in individuals suffering from severe depression, schizophrenia, or extreme sleep deprivation. 1 000 yard stare