PTSD is a medically accepted psychological disorder that has a very specific criteria which describes a very specific condition. However, that's not how the average person sees it.
PTSD is caused by suffering a trauma that is outside the standard human experience, and it has a set of specific symptoms. It isn’t “just” being very sad over an event in your life. Please understand that I’m not trying to minimise anyone’s pain, and I know that what is the breaking point for one person will be different from the next. I’m simply concerned over what appears to be a trend, and a general loosening of the word. I have felt sick upon seeing comments on Twitter such as “omg I’ve had such a bad day I think I have #PTSD” – really not cool.