What is borderline personality disorder?

Borderline personality disorder is a serious mental illness that affects how a person feels about themselves and others and makes it hard to function in everyday life.

It’s a condition defined by intense emotional dysregulation, unstable behavior, and a shifting self‑image that invades daily life and relationships. The term borderline originally referred to an outdated idea that people with the condition sat between neurosis and psychosis, but today it’s understood as a distinct disorder of emotional intensity and relational instability, sometimes called emotionally unstable personality disorder.

Although professionals still don’t know the exact origins of the disorder, research points to a mix of genetics, differences in brain‑structure, and childhood trauma or neglect. Treatment focuses on psychotherapy, especially Dialectical Behavior Therapy (DBT), which helps individuals regulate emotions, reduce self‑harm, and build more stable relationships.

What are the signs and symptoms?

People with BPD often experience intense mood swings and uncertainty about how they see themselves. Their interests, values, and feelings can change quickly.

People with BPD often struggle with fear of abandonment, rapidly changing relationships, a shifting identity, impulsive actions, self‑harm or suicidal behavior, and a persistent sense of emptiness. They most likely have an acute sensitivity to rejection, feelings of alienation, and a distorted self-image. Most people face intense and irregular moods, with episodes lasting from hours to days. Sometimes they may have problems controlling their anger or suffer feelings of dissociation, such as being cut off from oneself, observing oneself from outside the body, or feeling disconnected from one’s surroundings.

Even further, some people engage in reckless behaviors, such as spending sprees, unsafe sex, substance use, dangerous driving, and binge eating.

How can I find help?

If you have concerns about your mental health, talk to a primary care provider. They can refer you to a qualified mental health professional.

The Substance Abuse and Mental Health Services Administration (SAMHSA) has information on borderline personality disorder’s causes, symptoms, and treatment.

You can learn more about getting help on the NIMH website. You can also learn about finding support and locating mental health services in your area on the SAMHSA website.

How can I help a loved one?

Supporting a loved one with borderline personality disorder involves learning about the condition, offering steady emotional support, and encouraging treatment. It helps to understand their medical plan, reinforce healthy routines, and support medication use exactly as prescribed while urging them to speak with a provider before making any changes. Family members can also promote structure through daily scheduling, take any comments about self‑harm or suicide seriously, and seek their own counseling (ideally with a different therapist) to better manage the challenges of caregiving and stay aligned with treatment goals.