Borderline personality disorder (BPD) is a cluster B personality disorder characterized by persistent difficulties with impulsivity, self-identity, affect, and interpersonal relationships beginning in youth.

Patients often suffer from anxiety about abandonment and self-worth. They engage in self-destructive behaviors such as substance use and self-injurious actions. Splitting is a common feature of their unstable relationships. Patients may have episodes of intense dysphoria or anger. These individuals are at higher risk for having histories of physical, sexual, or emotional abuse during childhood. Patients with BPD may also have coexisting anxiety, depression, or another mental illness.

BPD is diagnosed more frequently in female patients than in males. The prevalence of BPD is estimated to be between 1.6% and 6% of the general population. It is most common among individuals with a first-degree relative who also has BPD or another psychiatric disorder. This condition often improves or becomes more stable in middle-aged patients.

A variety of pharmacologic and psychotherapeutic methods are used to treat BPD. Patients with BPD often suffer from the disease for a lifetime. Suicide, social and legal troubles, and frequent need for psychiatric and medical intervention can be common.

Patients with this disorder may have an increased risk of various general medical conditions.