A combination of personal history and biology appears to play a role in most personality disorders. Genetics play a significant — but not necessarily singular — role in the development of schizotypal, schizoid and paranoid personality disorders, which all are more common in families with a history of schizophrenia. Heredity also contributes to the development of obsessive-compulsive personality disorder.

A family history of antisocial personality disorder increases your risk of developing the condition, but childhood trauma also has considerable influence. Children with an alcoholic parent, or who have an abusive or chaotic home life, are at increased risk of developing antisocial personality disorder.

People with borderline personality disorder report the highest rate of childhood abuse — especially sexual abuse — at the youngest age, compared with that of other personality disorders. Many people with borderline personality disorder also have received a diagnosis of post-traumatic stress disorder. Heredity and childhood head injury also may influence the development of this disorder.

The causes of narcissistic, histrionic, avoidant and dependent personality disorders have been minimally studied and aren't yet well understood.

More women than men develop avoidant, borderline, dependent and paranoid personality disorders. Men are much more likely than women to have antisocial personality disorder and obsessive-compulsive personality disorder.

Other risk factors for personality disorders include:

• A history of childhood verbal, physical or sexual abuse
• A family history of schizophrenia
• A family history of personality disorders
• A childhood head injury
• Being a young adult
• Being divorced, separated, widowed or never married
• Having low socioeconomic status

People with personality disorders don't often realize that they need medical treatment. They're most likely to receive a diagnosis when they see a doctor for symptoms related to their disorder, such as depression and substance abuse, or when family and friends ask them to get help.

If someone you care about consistently behaves in a socially inappropriate way — for example, displaying excessive emotion, self-involvement, detachment or dependency, or harming others without showing remorse — consider suggesting that the person see a doctor to discuss how to deal with his or her emotions.

There are no specific tests for personality disorders. Your doctor will ask you questions about your symptoms, personal history and emotional well-being, and may talk to friends and relatives about your behavior. A mental health professional will probably help make the diagnosis, and he or she also will evaluate whether you have other mental health or substance abuse problems.

Doctors regard the diagnosis of most personality disorders in adolescents as premature. That's because what appear to be signs or symptoms of personality disorders often disappear as adolescents grow older. However, signs and symptoms of antisocial personality disorder become evident before age 15.

People with personality disorders are at significantly increased risk of:

• Social isolation. An inability to forge and maintain healthy relationships, lack of desire for closeness, or extreme shyness may cause those with personality disorders to be socially disconnected.
• Suicide. The risk of self-inflicted injury and suicide is highest among people with cluster B personality disorders, including histrionic, narcissistic, antisocial and borderline personality disorders.
• Substance abuse. Those with cluster B personality disorders are at especially increased risk of alcohol and drug addiction.
• Depression, anxiety and eating disorders. People with all types of personality disorders are at increased risk of developing other psychiatric problems.
• Self-destructive behavior. People with borderline personality disorder are particularly at risk of engaging in dangerous behaviors such as risky sex and gambling. Those with dependent personality disorder — who may tolerate mistreatment in order to stay in a relationship — are at increased risk of physical, emotional and sexual abuse.
• Violence and homicide. Aggressive behavior is a significant risk among those with paranoid and antisocial personality disorders.
• Incarceration. People with antisocial personality disorder are at increased risk of committing serious crimes. The condition is common among prisoners.

The intensity of the symptoms of personality disorders may change over time. The symptoms of cluster A and cluster B personality disorders may become less severe later in life. Those with cluster C personality disorders often experience worsening symptoms as they age.

A number of barriers make personality disorders among the most challenging mental health conditions to treat. People with these conditions are likely to have difficulty opening up to or retaining closeness with therapists. Perceived criticism may cause them to react angrily and break off therapy. Those who seek treatment on their own and who are motivated to stick with therapy over many years are the most likely to succeed.

Treatment for most personality disorders is with a combination of therapy and medications.

Therapy
Types of therapy that can help people with personality disorders include:

• Psychodynamic psychotherapy. This approach entails talking about your condition and related issues with a mental health professional. Psychotherapy can help people with personality disorders recognize how they're responsible for the turmoil in their lives and learn healthier ways of reacting to people and problems. Individual, group and family therapy can all be helpful.
• Cognitive behavior therapy. This form of psychological treatment involves actively retraining the way you think about problems, which in turn improves your emotions and behaviors.
• Dialectical behavior therapy. This type of cognitive behavior therapy focuses on coping skills — learning how to take better control of behaviors and emotions with techniques such as mindfulness, which helps you observe your feelings without reacting. It is most often used to treat borderline personality disorder. Doctors are studying the effectiveness of this type of therapy with all types of personality disorders.

Medication
People with personality disorders often experience serious mental and emotional strain, causing additional mental health problems such as depression, phobia and panic. Medications may help alleviate these related conditions, but they can't cure the underlying disorder. Therapy aimed at building new coping mechanisms must be the cornerstone of treatment.

Medications that may offer support during therapy include:

• Antidepressants. Doctors commonly prescribe selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine (Prozac, Sarafem), sertraline (Zoloft), citalopram (Celexa) and paroxetine (Paxil) or the related antidepressant venlafaxine (Effexor) to help relieve depression and anxiety in people with personality disorders. Less often, monoamine oxidase inhibitors such as phenelzine (Nardil) and tranylcypromine (Parnate) may be used.
• Anticonvulsants. These medications may help suppress impulsive and aggressive behavior. Your doctor may prescribe carbamazepine (Carbatrol, Tegretol) or divalproex (Depakote). Your doctor may also prescribe topiramate (Topamax), an anticonvulsant that's being studied as an aid in managing impulse-control problems.
• Antipsychotics. People with borderline and schizotypal personality disorders are at risk of losing touch with reality. Antipsychotic medications such as risperidone (Risperdal) and olanzapine (Zyprexa) can help improve distorted thinking. For severe behavior problems, doctors may prescribe haloperidol (Haldol).
• Other medications. Doctors sometimes prescribe anti-anxiety medications such as alprazolam (Xanax) and clonazepam (Klonopin) and mood stabilizers such as lithium (Eskalith, Lithobid) to relieve symptoms associated with personality disorders.

Living with someone who has a personality disorder can be very difficult. Remember that people with personality disorders are rarely aware that they have a problem. If you can gently help your loved one recognize that he or she needs help, improvement is possible.

Treatment progress can be bumpy, slow and painful. Try to be patient, and try not to take personally the mistreatment you may receive from your loved one. It's important to be supportive, but not at the expense of your own well-being. Nurture friendships and outside activities, and put self-care first.