Although originally believed to be on the "borderline" of psychosis, borderline personality disorder (BPD) is instead a disorder of emotion regulation. It is characterized by an enduring pattern of:
- Intense, but short-lived episodes of anger, depression and anxiety,
- Bouts of aggression, self-injury and drug or alcohol abuse,
- Feelings of being unworthy, misunderstood, mistreated, empty or unsure of who one really is,
- Sensitivity to rejection,
- Volatile relationships,
- Impulsive behaviors like excessive spending, binge eating and risky sex.
A type of psychotherapy called dialectical behavior therapy, which was developed specifically for the treatment of borderline personality disorder, is often used to treat it. Antidepressants and antipsychotics may be prescribed as well.

