It includes an implied aetiology in it's definition that renders all debate on aetiology tautological. It creates an arbitrary cut-off point in the scale of severity of trauma, which moves from edition to edition. It diminishes human variability and the powers of resilience and recovery. It is a retrograde step in the development of a humanistic, holistic science of persons. The truth is that reactions to trauma can certainly be severe and debilitating.
Some vulnerable people get big reactions from smaller traumas.
Some tougher people only get reactions from bigger traumas. The context is often important. The matter is very complex, and often uncertain. That is not the case. I will try to explain some key concepts.