Borderline personality disorder (BPD) is a serious mental illness characterized by pervasive instability in moods, interpersonal relationships, self-image, and behavior. This instability often disrupts family and work life, long-term planning, and the individual's sense of self-identity. Originally thought to be at the 'borderline' of psychosis, people with BPD suffer from a disorder of emotion regulation. While less well known than schizophrenia or bipolar disorder (manic-depressive illness), BPD is more common, affecting 2 percent of adults, mostly young women.