I think we do a dis-service trying to figure out what the differences are between a WAS and an MLC however that is just my opinion. Trying to diagnose a spouse and to know what is going on in their head is mostly mind reading. Their are so many other factors that can be at play that are all undiagnosed.
My mother is bipolar and during her mid life crisis never had another person, left my father and her bipolar got much worse, to the point of un-controllable. Now later in life she is still bipolar but older and slower. Depression in the U.S. can effect millions of people and mostly is under reported and untreated.
Childhood issues certainly play a part in MLC, however most of that happens before most of us meet our partners, so how do you know if they will rear their ugly heads later in life. Their is much more similarity between the two types MLC and WAS than their are differences. Best to just to keep the focus on ourselves, anything else is also non-productive and not really in the spirit of DB.