The term "shell shock" originated from WWI and was used to describe a range of psychological and neurological disorders that resulted from combat. However, this term has since been replaced, and its scope expanded with the current term, PTSD, and there are refined criteria for diagnosing this disorder.

Battle Fatigue or Combat Stress Reaction (CSR)\n\n In World War II, the shell shock diagnosis was replaced by Combat Stress Reaction (CSR), also known as "battle fatigue." With long surges common in World War II, soldiers became battle weary and exhausted.