Diagnosis of borderline personality disorder requires clinical assessment by a qualified mental health professional. Diagnostic criteria include intense fear of abandonment, a persistently unstable self-image, a pattern of unstable relationships veering between extremes of idealization and devaluation, impulsive risky behavior, suicidal or self-injurious behavior, frequent mood swings, chronic feelings of emptiness, difficulty controlling anger, and paranoid thinking or dissociative symptoms.

For a diagnosis, five or more of the criteria must be present, no later than early adulthood.