This question comes up quite often. If you review the symptoms of borderline personality disorder (BPD), lying is nowhere to be found. So, the short answer is, no, lying is not “officially” a part of BPD, and there has been no research on the topic, so there is no solid scientific evidence that lying is or isn’t associated with BPD.
Many family members and friends, however, cite lying as a major concern in their relationship with their BPD loved one. There are a number of reasons that someone with BPD may be more prone to lie.
BPD is associated with impulsivity (the tendency to do things without thinking about the consequences), so some instances of lying may be the result of a person with BPD just not thinking before giving a response.
In addition, people with BPD often experience deep and entrenched shame; lying may be one way to conceal mistakes or weaknesses that increase shameful feelings. People with BPD are often also very sensitive to rejection, so one function of lying could be to “cover up” mistakes, so that others will not reject them.
It can be difficult to maintain a relationship with a sibling with BPD; however, it is very important to understand that people with BPD often engage in destructive behaviors not because they intend to hurt you, but because their suffering is so intense they feel they have no other way to survive. Lying may be one example of this.
Kreger R. The Essential Family Guide to Borderline Personality Disorder. Center City, Minnesota: Hazelden, 2008