Post History
You portray the mood-swings of a character with BPD believably in the same way that you portray any other emotion of any other character believably – by motivating the emotions. The mood-swings o...
Answer
#3: Attribution notice added
Source: https://writers.stackexchange.com/a/47180 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#2: Initial revision
You portray the mood-swings of a character with BPD believably in the same way that you portray any other emotion of any other character believably – ### by motivating the emotions. The mood-swings of persons with BPD aren't random but triggered by outside events and motivated by internal thoughts, memories, needs, fears, and so on. For example, when a person with BPD _reacts_ to their loved one wanting to go to a party with a dramatic outburst of jealousy, hatred, and self-degradation, this is caused by that person's fear of loss, ambivalence towards their loved one, and their low self-esteem. How exactly the internal process works in your character is something you will have to make up (depending on the needs of your story) or research (looking at case studies in psychological publications) and write in whatever way fits your narrative style and target audience.