A sure-fire way to destroy your relationship is to diagnose your partner with a personality disorder or other character disease. Unfortunately, a cottage industry of self-help books exists to encourage you to do just that. Some are written by advocates or "survivors," who describe how you should react to your partner, using incendiary and contemptuous adjectives, such as "congenitally manipulative, opportunistic, cunning, exploitive, wolf in sheep's clothing, etc." Others are written by therapists who psychoanalyze your partner with various interpretations of why he/she makes you feel bad. Both types describe the insidious behavior of the PD, not so much to inform and enlighten as to appeal to the reader's victim-identity and self-righteousness. They typically supplement their superficial descriptions with general symptom checklists, without emphasizing that a preponderance of those - not just a few -- are necessary for a valid diagnosis and that a valid diagnosis must come after careful, objective examination.
These days a book has a good chance of making the best-seller list if it comes up with a new way for the reader to feel like a victim and justify the sense of entitlement that goes with victimhood. Such books allow readers to substitute easy pity for genuine compassion, only to be caught in an inevitable pity-contempt-guilt-pity pendulum of pain.
Unfortunately, it's not just self-help books that contribute to emotional pollution. The desire to hook clients into psychotherapy sometimes overrides the ethics of therapists who diagnose their clients' partners, based entirely on third-party descriptions. I have had more than two dozen couples referred to me in the past year alone who were each diagnosed by their partner's individual therapist with a personality disorder. The most common combination, of course, is a narcissistic man married to a borderline woman, though variations have come from more creative therapists with the temerity to diagnose without examination. In no case were these third-party diagnoses valid or helpful.
Complementary diagnoses have become common because the motivation to diagnose loved ones is neither to understand nor sympathize, but to blame from a position of moral superiority—a powerful driving force in the age of entitlement.
While self-help authors who encourage readers to diagnose their partners are out to sell books, I suspect that many therapists who diagnose without examination are trying to counter the propensity of some clients to blame themselves for the poor behavior of their partners—"It's not your fault!" is the mantra of the poorly trained. But there's little doubt that the utter powerlessness engendered by blaming will keep their hapless clients in treatment for quite some time, to the financial benefit of the therapist.
Personality disorders are extremely complex diagnoses that only a professional should make after thorough examination and testing of the subject, supplemented by interviews with the partner. The diagnosis cannot be made by a self-help book or advocate or by a therapist going exclusively on the highly subjective descriptions of a hurt, distressed, or resentful client.
If you have an urge to diagnose your partner, you cannot at the same time have genuine self-compassion, which would give you insight into your pain, along with motivation to heal and improve; blame neither heals nor improves. Neither can you experience the genuine compassion for your partner that would give you insight into his/her deeper experience, which is necessary to evaluate the possibility that he/she can heal and improve. The urge to diagnose makes you see yourself and other people too superficially to do anything but harm to your relationship.
If you truly believe you are married to a personality disorder, you should leave the relationship before your pity-contempt-guilt-pity pendulum swings make him/her angrier and still harder to live with. However, you would be better served to burn any self-help book and fire any therapist or advocate who diagnoses your partner unseen.
Instead of diagnosing, try to understand your partner's experience of you and of the world. The only way to judge the emotional reality of your relationship is to hold his/her perspective alongside your own. One perspective of your relationship, even when it is right, is incomplete. Relationships must have binocular vision to flourish.
You do not need a diagnosis to evaluate your relationship. All you need to determine whether it is viable and repairable is to feel as much compassion from your partner as you give and to know, through your binocular vision, that your partner sees your perspectives as equal to his/her own.