system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is Borderline Personality Disorder?

Friend I grew up with was just diagnosed with BPD.  What is it?  Is that why he never got along with his family?
gpt
It is a mental health diagnosis that does impact people's ability to maintain close and long term relationships including family, friends and lovers. While there are several criteria and characteristics a few significant ones reported by many suffers include:

1) The feeling that there is a "hole" inside of them that needs filling

2) The thought that a close intimate relationship will fill that hole

3) Hot and cold running emotions toward people close to them, the swings from "you are the greatest person ever" to "you are trying to destroy me" can be sudden, frequent and seeming unprovoked. 


These things (and a few other) conspire to keep the person out of long term relationships and hopping from intense relationship to intense relationship in that constant search to fill the "hole".