That is such a good point. I have thought about that a lot too. I have even read a "little" bit about it. Haven't seen too much information on it. Maybe it should be researched a little more.
My mom's hit the fan in spades about 11-12 years ago. Her bpd/npd mother had just died and she and all of her siblings had taken turns taking care of her at home. According to my mom her mom's last words to her were -"insert mom's name here

leave me alone." Which of course would be devastating, but now I wonder if it even happened. Then we moved 1200 miles away - a year later they moved here. So lots of big things happened. But in the last few years, it has continued to get bad, not level off or anything. She really didn't have much of a relationship with her mom. They weren't close at all. So who knows.