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Does My Sister Have Borderline PD?

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My sister has many symptoms of someone who suffers from borderline personality disorder — she feels lost, and doesn’t know what direction she needs to go in life. In the last six months, she has come up with different things she wants to be when she grows up (she’s in her forties). This has been a pattern in her life. She catastrophizes many events in her life — “this is the worst thing that could ever happen,” I’ve heard that from the car accident to remodeling the kitchen. She has cut off relationships at the drop of a hat, never to speak to people again. She gets angry very quickly and when slightly challenged or confronted, will cut you off quickly, either by hanging up on you or leaving.

If you apologize for making her upset, there is no acknowledgment on her part that she has done anything wrong, and an indifference towards the apology in general. She has had many many jobs, none for very long, and many relationships (one marriage lasted 10 years). She is quick to share her suffering, but if you try to share something with her of a similar nature, she is cold and unempathetic, and at times harsh with criticism over your own feelings.

I’m at a loss what to do with her or how to help. She seems to only want me for a sounding board, which I usually provide because to do otherwise results in alienation for a period of time. I think the only reason she hasn’t cut me out of her life like she has other people is because we are family. I’ve suggested therapy in the nicest way I could, but it was dismissed fairly quickly.

She is not self- destructive, i.e. no cutting or suicidal tendencies. She does have issues around eating, although she swears she does not have an eating disorder. She seems to have many of the symptoms of borderline, but not all. How do you determine if someone is or isn’t borderline?

Does My Sister Have Borderline PD?

Answered by on -


A person has borderline personality disorder if they meet a certain number of clinical criteria including many of the symptoms that your sister displays. However, only a trained clinician who met with your sister in person would know for sure if she suffers with this disorder, and like you mentioned, it is unlikely that she would attend such an evaluation.

Even if your sister would attend an evaluation and seek treatment, it may take a long time for her to change. Even the best treatments for borderline personality disorder can take months to years to help a person get a handle on their symptoms and alter their long-standing pattern of behavior. The bottom line is that even if she is successful at changing her behavior, it could take a long time for you to notice a marked improvement.

Because of this my suggestion is that you will likely need to learn better ways to deal with your sister. This means that you will have to change your behavior towards her. For instance, you mentioned that she only seems to want you as a sounding board to which you provide for her at her request. This is a big mistake and is particularly unhealthy for you and an incorrect way to deal with her. It sounds like you have to “walk on eggshells” whenever she is around. You do this because you do not want to lose her but the problem is that you are essentially letting her abuse you or act inappropriately towards you. She in essence is getting away with acting a certain way towards you, in an abusive and inappropriate way because she can get away with it from you.

It would be better for you to define when you are going to be there for her and it should not be when she demands that you be there. You can be there for her when you are available — on your time — and when she can learn to talk and treat with you with more respect and not make unreasonable demands, yell or scream or act out inappropriately. You should not have to “walk on eggshells” around your sister and the way to stop this is to better define how she can interact with you. If you do this successfully and in time, you will change the dynamic of your relationship with her. You will not cure her (if she has an illness such as borderline personality disorder) but you will have a better and potentially more stable relationship with your sister.

Finally, let me warn you that if you begin to change the way you interact with your sister (i.e. you no longer be her sounding board whenever she demands) this will anger her at first. To be successful in permanently changing the way you interact with her, you will need to let her be angry with you. In time, her anger will decrease and she will ultimately learn this new way of dealing with you on your terms.

I hope this helps answer your question or gives you at least a little insight on how to deal with difficult and unreasonable people. Please write back if you have any more questions or need clarification. Take care.

Does My Sister Have Borderline PD?

This article has been updated from the original version, which was originally published here on November 7, 2007.

Therapists live, online right now, from BetterHelp:

Kristina Randle, Ph.D., LCSW

Kristina Randle, Ph.D., LCSW is a licensed psychotherapist and Assistant Professor of Social Work and Forensics with extensive experience in the field of mental health. She works in private practice with adults, adolescents and families. Kristina has worked in a large array of settings including community mental health, college counseling and university research centers.

APA Reference
Randle, K. (2019). Does My Sister Have Borderline PD?. Psych Central. Retrieved on December 5, 2020, from
Scientifically Reviewed
Last updated: 22 May 2019 (Originally: 7 Nov 2017)
Last reviewed: By a member of our scientific advisory board on 22 May 2019
Published on Psych All rights reserved.