Borderline personality disorder (BPD) is characterized by a painful mix of emotional turmoil, unstable relationships and self-image, and self-destructive impulsivity. People with the disorder are volatile, hard on those close to them and quick to feel abandoned or betrayed. They are at high risk for dangerous or suicidal behavior.

Until recently, borderline personality disorder wasn't diagnosed in anyone under 18. But new understanding of the disorder has changed that, and more effective treatments have greatly improved the prognosis for someone with BPD. Experts now stress that symptoms develop in adolescence, and treating BPD as early as possible leads to better long-term outcomes.

BPD is more common among those who have first-degree relatives with the disorder. Experts call it a biosocial disorder because it is the result of two distinct factors, biological and social. The biological factor in BPD is a temperament that is highly emotionally reactive, quick to get very upset and slow to return to baseline. The social factor is being raised in an environment that does not validate those intense emotions in childhood, either through neglect or ordinary parenting practices that dismiss extreme emotions as overreactions. Without that validation from adults, children may not develop effective skills in emotional regulation, and may instead resort to unhealthy ways of coping with their feelings.

Diagnosis of borderline personality disorder requires clinical assessment by a qualified mental health professional.

Diagnostic criteria include:

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

There are several specialized forms of therapy that have been developed to treat borderline personality disorder, but the treatment with the strongest evidence for its effectiveness is called dialectical behavioral therapy, or DBT. It's called "dialectical" because it involves two things that might seem to be in opposition but are both important: the need for acceptance and the need for change.

First, a patient's feelings are validated, or accepted without judgment. Once he feels understood and supported, he is able to learn more effective ways to manage and respond to those feelings. Skills taught in DBT include coping with difficult situations, distress tolerance and interacting more effectively with others.

Other types of psychotherapy that have been found to be effective in treating the disorder include mentalization-based therapy, schema-focused therapy and transference-focused therapy.

Medications, including antidepressants, antipsychotics and anti-anxiety drugs, can't treat borderline personality disorder, but they may prove helpful in treating co-occurring disorders such as depression, impulsiveness or anxiety.

Hospitalization may be required for more intense treatment of adolescents or young adults who are at risk of self-injury or suicidal behavior.

It is not uncommon for people with borderline personality disorder to struggle with more than one disorder. Depression, bipolar disorder, substance use disorder, eating disorders and trauma are frequently seen with borderline personality disorder.