I think that the overlap in symptoms makes it difficult. Some might be because overwhelmed brains use the same defense mechanisms for different sources of overwhelmingness sometimes.
"Dissociation" and "shutdowns" for instance... lots of overlap in how people describe these; could be using the same mechanism even if the precise parts of brain affected might differ a little. I think it's like a circuit breaker to shut down reactions to parts of one's world, try to keep functioning somewhat. (I know sometimes it prevents functioning, but lots of bodily mechanisms can go to far.) Mine has always been partial and I didn't understand its environmental sensory sources for years, whichever word one uses.
