Borderline Personality Disorder (BPD) is a serious mental illness marked by unstable moods, behavior, and relationships. In 1980, the Diagnostic and Statistical Manual for Mental Disorders, Third Edition (DSM-III) listed BPD as a diagnosable illness for the first time. Most psychiatrists and other mental health professionals use the DSM to diagnose mental illnesses.
Because some people with severe Borderline Personality Disorder (BPD) have brief psychotic episodes, experts originally thought of this illness as atypical, or borderline, versions of other mental disorders. While mental health experts now generally agree that the name “borderline personality disorder” is misleading, a more accurate term does not exist yet.