What Exactly Is Borderline Personality Disorder—and How Do You Know If You Could Have It?

The mental illness may affect as many as 6% of a population, most of them women.

Borderline personality disorder is a mental illness that seems to emerge mostly in late adolescence and early adulthood. Many people can experience remission, but the disorder can continue over a lifetime and can cause significant problems in two main areas of life: a sense of self and relationships.

“It will begin to interfere with your capacity to be happy, to be clear about who you are and what you’re going to do in life, and to be able to navigate the world socially and occupationally,” John M. Oldham, MD, past president of the American Psychiatric Association, tells Health.

According to the National Alliance on Mental Illness, an estimated 1.6% of Americans have borderline personality disorder (BPD), but the real number may be as high as 5.9%. Most of these are women, although experts believe that many men who actually have borderline may have been misdiagnosed with other conditions.

Borderline personality disorder symptoms

People with borderline personality disorder experience emotions, including anger, very intensely, with up-and-down mood swings that can last hours or days. Often the swings are triggered by events that might seem completely insignificant to someone without the disorder.

“They can be very easily set off in an emotional storm and have trouble navigating the world because they’re so thin-skinned and reactive,” says Dr. Oldham, who is also interim chief of staff at The Menninger Clinic in Houston. “They have an emotional motor that’s easy to kick into overdrive and that runs hot at the very littlest precipitant.”

Maybe a phone call isn’t returned or a new acquaintance doesn’t seem friendly when, in fact, the other person is simply preoccupied. The person with BPD may become convinced that the other person is being critical and doesn’t like them and then become overtly hostile, maybe even picking a fight.

“When the borderline person behaves that way, it spooks the other person,” says Dr. Oldham. “They try to be reasonably friendly, but they keep encountering hostility and it ends up being a self-fulfilling prophecy.”

Not only is the engine running super fast, the “brakes” in a person with borderline also don’t work. “The part of the brain that has regulatory function and can control emotions … is very weak,” says Dr. Oldham. “[People] often think the person [with borderline] is behaving in a deliberate, willful way, but actually they don’t know how to stop.”

People with borderline personality disorder often act impulsively and even self-destructively. They may cut or burn themselves, go on spending sprees, have unsafe sex, use drugs or alcohol, or even attempt suicide to try to shut down the circuits.

People with this disorder also lack a strong sense of self. Instead, they adopt transient identities that reflect the people and circumstances around them. That means their values, goals, and opinions can change on a whim.

“They don’t have a well-established, mature sense of who they are,” says Dr. Oldham. “Patients with borderline will admire somebody and be overly solicitous and compliment them, then when any little thing happens, that flips the switch and they go completely to the opposite end of the spectrum and will be absolutely enraged at this person and critical and hostile.”

Often, a fear of abandonment and rejection drives some of this behavior in people with borderline personality disorder.

Borderline personality disorder causes

No one knows exactly what causes borderline personality disorder but, like so many other physical and emotional conditions, it seems to be a combination of genetics and environment. People with a family history of BPD are much more likely to have the condition. And many people with BPD have also suffered childhood trauma.

Genes set up your likelihood of being a certain way, says Dr. Oldham, “and that can be altered and move into a good direction or a troubled one depending on trauma or challenges developmentally.”

Fortunately, a genetic predisposition doesn’t mean a borderline diagnosis is inevitable. “The heritable risk is about the same as breast cancer,” Dr. Oldham says. “It has a risk, but it doesn’t mean you’re going to encounter the turbulence to precipitate the illness.”

Research also shows that people with the disorder have changes in the brain, particularly the areas that control impulses and regulate emotions, but it’s not clear if the changes are a result or a cause of BPD.

Borderline personality disorder treatment

The mainstay of treatment for borderline personality disorder is psychotherapy. This is unlike most other psychiatric conditions, like anxiety or depression, where medication is usually called for, says Dr. Oldham. Therapy can be one-on-one with a professional or in a group setting. Certain types of psychotherapy seem to be especially helpful for BPD.

Dialectical behavior therapy is often the first choice for psychotherapy for BPD. The method was actually developed to treat borderline personality disorder and teaches skills—many of them based on mindfulness techniques like meditation—to manage emotions and interact with others.

Cognitive behavioral therapy (CBT) has also shown success in patients with borderline personality disorder. CBT focuses on changing core beliefs about yourself with the idea that this will help change behaviors based on negative misperceptions.

Other therapies that have been effective in treating BPD include schema-focused therapy, mentalization-based therapy, systems training for emotional predictability and problem-solving, and transference-focused psychotherapy, according to the Mayo Clinic.


Usually therapy is done while the person is living on their own and with the goal of helping them stay in their community. People with borderline personality disorder sometimes need to be hospitalized for short periods of time, usually when they are behaving impulsively or threatening to harm themselves.

One of the main challenges of treatment for borderline personality disorder is sticking with it, especially given that the borderline patient may suddenly decide they dislike their therapist or that the therapist is being critical.

“People can do well in treatment over time, but it takes time and work and effort,” says Dr. Oldham. Years of therapy could be necessary.

No drugs have been approved specifically to treat BPD, but medications typically used for other disorders can help, such as antidepressants. Many people with BPD also have other mental health disorders—such as depression, anxiety, or PTSD—which do require medication.

A psychotherapy-focused treatment plan can help people get on with their lives. “Borderline personality disorder is not a life sentence,” says Dr. Oldham. “Patients can learn when to avoid things that are likely to set them off and, once they practice that, can get to a much better place. They can stabilize their functioning. They do improve.

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