Causes and risk factors of personality disorders

If you or someone you love has a personality disorder, one question often comes up fast: why did this happen? Many people blame themselves. Many parents blame themselves too. The real answer is more kind, and more complicated, than blame.

No one knows the exact cause. Research points to a mix of inherited traits, a sensitive temperament, early life experiences and later stress. This page explains each piece in plain words. It uses borderline personality disorder (BPD) as the main example, because it is the most studied. Read the overview of personality disorders for the big picture.

Is a personality disorder anyone's fault?

No. A personality disorder is a health condition, not a character flaw or a choice. A child does not choose a sensitive nature. Most parents do not choose to hurt their child either. Some families face poverty, illness, war or their own untreated pain, and that stress reaches the children.

Experts describe the causes as a mix of genes and life experiences. Genes may make a person more likely to develop one, and life events may set it off.⁵ Because it is a mix, no single person or event can be named as "the cause."

Genes and family history

Personality disorders run in some families. Having a parent or sibling with BPD or a similar condition raises a person's risk.^1,4 But no single "BPD gene" has been found.³

Twin studies help tell genes apart from upbringing. In one study of 7,233 twins and siblings aged 18 to 90, about 45% of the differences in borderline traits were linked to genes. The rest were linked to each person's own life experiences.⁷ That is a moderate share, not the whole story.

Another study followed 2,282 Norwegian twins for about 10 years, from early adulthood into midlife. Borderline traits stayed fairly steady over that time, and genes explained most of that steadiness. The effects of life experiences changed a lot from one period to the next.⁸ This fits what many people notice in daily life: symptoms rise and fall with stress and support.

Genes may work through broad traits, not through "borderline" itself. In the same study, the genetic risk for borderline traits overlapped heavily with the genetic risk for antisocial traits.⁸ A separate study found that borderline traits and adult ADHD symptoms share both genes and life experiences, which may be one reason the two often appear together.⁷ See adult ADHD and getting a careful diagnosis.

Temperament: the way a person is wired

Temperament is the emotional style a person is born with. Some babies are calm. Others react strongly and take longer to settle down. Neither is bad, but a very sensitive child may need more help learning to handle big feelings.

Researchers have linked several childhood traits to a later risk of BPD: strong negative feelings, quick mood shifts, acting on impulse and low self-control.⁹ A mix of traits such as avoiding harm, seeking thrills and weak impulse control is also listed as a risk factor for personality disorders in general.⁵

The brain and emotions

Brain imaging studies suggest that in people with BPD, the areas that control impulses and regulate emotions may work differently. Scientists do not yet know whether these differences raise the risk or result from living with the disorder.¹ One description is that brain areas that handle emotion and decision-making may not talk to each other as smoothly as they could.³

This does not mean the brain is "broken." Skills-based therapy such as DBT teaches ways to handle strong emotions.

Childhood hardship and trauma

Many people with BPD report hard experiences in childhood. These include physical, emotional or sexual abuse, neglect, and being separated from a parent or caregiver.^3,4 Other risks are caregivers who struggled with substance use or mental illness, and homes marked by anger and conflict.⁴

A research review of early risk factors found that the strongest links were with verbal, physical and sexual abuse, a parent who was emotionally withdrawn or neglectful, and being bullied by peers over a long time. Family hardship, low income and a parent with BPD also raised the risk.⁹

Trauma and personality disorders often overlap with other conditions, such as post-traumatic stress disorder (PTSD).² They are not the same thing. Read more in our pages on PTSD and trauma and who develops PTSD.

Invalidation: when feelings are not heard

Many clinicians use a "biosocial" model, first described by psychologist Marsha Linehan, who created DBT. It says BPD grows from two things working together over time. The first is a person's built-in emotional sensitivity. The second is an invalidating environment.¹⁰

To invalidate means to brush off, ignore or punish a person's feelings. Examples are "You're overreacting," "Stop crying, it's nothing," or harsh criticism for showing emotion. Abuse is the most extreme form. Quieter forms count too, such as a home where strong feelings are not allowed.¹⁰

Here is how the model says the cycle works. A sensitive child has big feelings. Adults around the child, often with no bad intent, do not know how to respond. The child never learns how to name feelings, calm down or trust them. Later, the child may turn to risky ways of coping to get relief.¹⁰

One study of university students in Singapore found that growing up with a mother who dismissed their feelings was linked to more BPD symptoms. The authors say this gives some support to the model across cultures, though it was one study in one group.¹⁰

The model is meant to explain, not to blame. Often, no one in the family knew another way. Parents of a very sensitive child can learn new skills too. See supporting someone with a personality disorder.

Why does it usually start in the teen years or early adulthood?

Personality forms early in life, and personality disorders usually begin in the teen years or early adulthood.^5,6 BPD is usually diagnosed in late adolescence or early adulthood. A young person under 18 can be diagnosed if symptoms are severe and have lasted at least a year.² Mayo Clinic notes that BPD is most severe in young adulthood.⁴

Doctors often wait to diagnose people under 18, even though the signs can be seen earlier.^9,12 This can delay help. One review found that borderline symptoms that begin before age 19 can predict problems with daily life years later, which is a good reason to get help early.⁹

Why then? The teen and young adult years bring big changes. Young people are forming an identity, making close relationships and facing new stresses, often with a brain still developing. For someone with an emotionally sensitive nature and little practice in coping, this can be a heavy load. This is a general explanation, and the research is still growing.

What this means for the outlook

Knowing the causes can give a sense of relief, but causes do not decide the future. Evidence-based treatments help many people have fewer symptoms and function better.¹ NAMI notes good long-term outcomes for people with BPD who take part in a full treatment plan.³

A long study of people first treated in the hospital for BPD found that most reached remission. By 16 years, between about 78% and 99% (depending on how remission was measured) had stopped meeting the criteria. About 1 in 10 to 1 in 3 had symptoms come back later. About 4 in 10 to 6 in 10 reached recovery, which means fewer symptoms plus good work and social life.¹¹ Anger, mood swings and impulsive acts often ease with age. Fear of abandonment and relationship struggles may last longer, but they can be worked on.⁴

Other personality disorders

Most research on causes has focused on BPD. For other personality disorders, such as the ones in Cluster A (odd or suspicious), Cluster B (dramatic or emotional) and Cluster C (anxious or fearful), experts also point to a blend of genes and early experiences.^5,6 Learn more about the other types.

Common questions

When to get help

• See a doctor or therapist if feelings, moods or relationships keep causing pain or problems. A careful assessment is the first step, and treatment can help.
• Call or text 988 any time you or someone you love is thinking about suicide or self-harm. It is free, private and open 24 hours a day.
• Call 911 if there is immediate danger.
• A safety plan made ahead of time can help in a hard moment. You can also visit our help page.

If you are older, see personality disorders in later life. A new change in personality after age 60 should always be checked by a doctor.

Education only. This page is general information written from the sources listed. It is not medical, legal or financial advice and does not replace a doctor, therapist or lawyer who knows your situation. How we write and check pages.