Hi Anna (fellow psychologist here):

Of the three thousand or so evaluations I've done, there are quite a few NPD and BPD dx's among them. I've always been inclined to minimize diagnostic classifications and look beyond to the unique person. And you're no doubt correct, many resist therapy due to the stigma of these diagnoses.

Two thoughts:

(1) While no doubt that the lens of trauma helps some, there are those with these traits (whether or not the full diagnosis) who simply have not had trauma in their lives. I find that looking at something THEY feel is positive in their lives, something they are having difficulty with, can be a way of connecting to them without having to use diagnoses OR the trauma lens

(2) We (my wife and I) have a relative with bipolar and who has been dx variously with not the full dx but traits of narcissism, borderline, paranoid, OCD and histrionic (avoidant and dependent as well, but those are no longer in the DSM). I've worked with her whole family over the years to encourage them to set firmer (but still loving, compassionate boundaries). It enabled my wife's mother to have a profound and joyful respite during the last years of her life, as my wife and I agreed to take responsibilty.

In the last year or so, my wife and I have established firm enough boundaries that the situation has become not just manageable but remarkably easy. And perhaps most important, we've ALWAYS left open the door - ANY time our family member wishes to talk in more detail about fulfilling those long-unfilled hopes and dreams, the door is completely open - with no pressure, no judgment, no demands.

TLDR:

(1) Finding in the person a positive calling rather than focusing on dx OR trauma can be helpful;

(2) loving, compassionate and appropriate boundaries can be essential when you find yourself connected to someone with NPD/BPD traits by obligation or responsibility.