Q. I myself am a therapist (MSW) very interested in cluster b personality disorders, particularly Borderline/Narcissists. they can be so similar and share many traits -How would/could you make a firm diagnosis of one or the other? I realize their can be a dual diagnosis but I am wondering if there is some definite quality/trait/characteristic that separates them.

  A. If the individual has both, they have both. Either personality is really a behavioral trait, just like a fever or achy joint is in any medical illness. In and of itself, neither fever or joint pain is enough to make a diagnosis. You treat based on all the symptoms making up the illness. Thus, narcissism with BPD or any other complaints is likely different from narcissism with BPD, OCD, depression, migraines, and irritable bowel. In most folks clinical experience, narcissism is a bad prognosticator for outcome since it is ego syntonic, and patients are not motivated to change an ego syntonic behavior as much as an ego dystonic one.