The essential feature of borderline personality disorder is a pervasive pattern of instability of interpersonal relationships, affects, and self-image, as well as marked impulsivity that begins by early adulthood and appears in a variety of contexts. These characteristics are severe and persistent enough to result in clinically significant impairment in social, occupational, or other important areas of functioning. Common and important features of borderline personality disorder are a severely impaired capacity for attachment and predictably maladaptive behavior in response to separation. Individuals with this disorder are very sensitive to abandonment and make frantic efforts to avoid real or perceived abandonment. They often experience intense abandonment fears and anger in reaction to even realistic time-limited separation. Efforts to avoid abandonment may include inappropriate rage, unfair accusations, and impulsive behaviors such as self-mutilation or suicidal behaviors, which often elicit a guilty or fearful protective response from others.

The relationships of individuals with borderline personality disorder tend to be unstable, intense, and stormy. Their views of others may suddenly and dramatically shift, alternating between extremes of idealization and devaluation, or seeing others as beneficent and nurturing and then as cruel, punitive, and rejecting. These shifts are particularly likely to occur in response to disillusionment with a significant other or when a sustaining relationship is threatened or lost.

The disorder is usually characterized by identity disturbance, which consists of markedly and persistently unstable self-image or sense of self. Self-image (goals, values, type of friends, vocational goals) may suddenly and dramatically shift. Individuals with this disorder usually feel bad or evil, but they may also feel that they do not exist at all, especially when feeling unsupported and alone.

Many individuals with borderline personality disorder are impulsive in one or more potentially self-damaging areas, such as spending money irresponsibly, gambling, engaging in unsafe sexual behavior, abusing drugs or alcohol, driving recklessly, or binge eating. Self-mutilation (e.g., cutting or burning) and recurrent suicidal behaviors, gestures, or threats are common. These self-destructive acts are often precipitated by potential separation from others, perceived or actual rejection or abandonment, or the expectation from others that they assume more responsibility.

Affective instability is another common feature of the disorder. This consists of marked mood reactivity (e.g., intense episodic dysphoria, irritability, or anxiety that usually lasts for a few hours and only rarely for more than a few days). The usual dysphoric mood of these individuals is often punctuated by anger, panic, or despair and is only infrequently relieved by periods of well-being. These episodes may be triggered by the individual's extreme reactivity to interpersonal stressors. Individuals with this disorder also typically have chronic feelings of emptiness. Many experience inappropriate, intense anger or have difficulty controlling their anger. For example, they may lose their temper, feel constant anger, have verbal outbursts, or engage in physical fights. This anger may be triggered by their perception that an important person is neglectful, withholding, uncaring, or abandoning. Expressions of anger may be followed by feelings of being evil or by feelings of shame and guilt. During periods of extreme stress (e.g., perceived or actual abandonment), these individuals may experience transient paranoid ideation or severe dissociative symptoms (e.g., depersonalization).

It is not necessary for an individual to have all of the above features for borderline personality disorder to be diagnosed. As indicated in Table 1, the diagnosis is given if at least five of the nine diagnostic criteria are present.

Transient psychotic-like symptoms (e.g., hearing their name called) may occur at times of stress. These episodes usually last for minutes or hours and are generally of insufficient duration or severity to warrant an additional diagnosis. Another common associated feature is a tendency for these individuals to undermine themselves when a goal is about to be reached (e.g., severely regressing after a discussion of how well therapy is going). Individuals with this disorder may feel more secure with transitional objects (e.g., a pet or inanimate object) than with interpersonal relationships. Despite their significant relationship problems, they may deny that they are responsible for such problems and may instead blame others for their difficulties.

Physical and sexual abuse, neglect, hostile conflict, and early parental loss or separation are more common in the childhood histories of those with borderline personality disorder than in those without the disorder.

Axis I disorders and other axis II disorders are often comorbid with borderline personality disorder. Among the most common comorbid axis I disorders are mood disorders, substance-related disorders, eating disorders (notably bulimia), PTSD, panic disorder, and ADHD. Such axis I comorbidity can complicate and worsen the course of borderline personality disorder. Commonly co-occurring axis II disorders are antisocial, avoidant, histrionic, narcissistic, and schizotypal personality disorders.

Borderline personality disorder is characterized by notable distress and functional impairment. A majority of patients attempt suicide. Completed suicide occurs in 8%–10% of individuals with this disorder, a rate that is approximately 50 times higher than in the general population. Risk of suicide appears to be highest when patients are in their 20s as well as in the presence of co-occurring mood disorders or substance-related disorders (87). Physical handicaps may result from self-inflicted injury or failed suicide attempts. These individuals often have notable difficulty with occupational, academic, or role functioning. Their functioning may deteriorate in unstructured work or school situations, and recurrent job loss and interrupted education are common. Difficulties in relationships, as well as divorce, are also common.

The social cost for patients with borderline personality disorder and their families is substantial. Longitudinal studies of patients with borderline personality disorder indicate that even though these patients may gradually attain functional roles 10–15 years after admission to psychiatric facilities, still only about one-half will have stable, full-time employment or stable marriages (40, 134). Recent data indicate that patients with borderline personality disorder show greater lifetime utilization of most major categories of medication and of most types of psychotherapy than do patients with schizotypal, avoidant, or obsessive-compulsive personality disorder or patients with major depressive disorder (135).

A skilled clinical interview is the mainstay of diagnosing borderline personality disorder. This approach should be complemented by knowledge of the DSM criteria and a longitudinal view of the clinical picture. The additional use of assessment instruments can be useful, especially when the diagnosis is unclear. Use of such instruments must be accompanied by clinical judgment.

Certain assessment issues relevant to all personality disorders should be considered when diagnosing borderline personality disorder. For the diagnosis to be made, the personality traits must cause subjective distress or significant impairment in functioning. The traits must also deviate markedly from the culturally expected and accepted range, or norm, and this deviation must be manifested in more than one of the following areas: cognition, affectivity, control over impulses, and ways of relating to others. Therefore, multiple domains of experience and behavior (i.e., cognition, affect, intrapsychic experience, and interpersonal interaction) must be assessed to determine whether borderline traits are distressing or impairing. The clinician should also ascertain that the personality traits are of early onset, pervasive, and enduring; they should not be transient or present in only one situation or in response to only one specific trigger. It is important that borderline personality disorder be assessed as carefully in men as in women.

The ego-syntonicity of the personality traits may complicate the assessment process; the use of multiple sources of information (e.g., medical records and informants who know the patient well) can be particularly helpful in establishing the diagnosis if the patient's self-awareness is limited. Given the high comorbidity of axis I disorders with borderline personality disorder, it is important to do a full axis I evaluation. An attempt should be made to distinguish axis I states (e.g., mood disorder) from borderline personality disorder, which can be a complex process. Useful approaches are to obtain a description of the patient's personality traits and coping styles when prominent axis I symptoms are absent and to use information provided by people who have known the patient without an axis I disorder. If axis I disorders are present, both the axis I disorders and borderline personality disorder should be diagnosed.

Because the personality of children and adolescents is still developing, borderline personality disorder should be diagnosed with care in this age group. Often, the presence of the disorder does not become clear until late adolescence or adulthood.

When assessing a patient with borderline personality disorder, the clinician should carefully look for the presence of risk-taking and impulsive behaviors, mood disturbance and reactivity, risk of suicide, risk of violence to persons or property, substance abuse, the patient's ability to care for himself/herself or others (e.g., children), financial resources, psychosocial stressors, and psychosocial supports (e.g., family and friends).

Borderline personality disorder often co-occurs with mood disorders, and when criteria for both are met, both should be diagnosed. However, some features of borderline personality disorder may overlap with those of mood disorders, complicating the differential diagnostic assessment. For example, the affective instability and impulsivity of borderline personality disorder may mimic features of bipolar disorder, especially bipolar II disorder. However, in borderline personality disorder, the mood swings are often triggered by interpersonal stressors (e.g., rejection), and a particular mood is usually less sustained than in bipolar disorder. Depressive features may meet criteria for major depressive disorder or may be features of the borderline personality disorder itself. Depressive features that appear particularly characteristic of borderline personality disorder are emptiness, self-condemnation, abandonment fears, self-destructiveness, and hopelessness (91, 92). It can be particularly difficult to differentiate dysthymic disorder from borderline personality disorder, given that chronic dysphoria is so common in individuals with borderline personality disorder. However, the presence of the aforementioned affective features (e.g., mood swings triggered by interpersonal stressors) should prompt consideration of the diagnosis of borderline personality disorder. In addition, the other features of borderline personality disorder (e.g., identity disturbance, chronic self-destructive behaviors, frantic efforts to avoid abandonment) are generally not characteristic of axis I mood disorders. In other cases, what appear to be features of borderline personality disorder may constitute symptoms of an axis I disorder (e.g., bipolar disorder). A more in-depth consideration of the differential diagnosis or treatment of the presumed axis I condition may help clarify such questions.

PTSD is a common comorbid condition in patients with borderline personality disorder and, when present, should be diagnosed. However, a history of trauma is often characteristic of patients with borderline personality disorder and does not necessarily warrant an additional diagnosis of PTSD. PTSD should be diagnosed only when full criteria for the disorder are met. PTSD is characterized by rapid-onset symptoms that occur, usually in adulthood, in reaction to exposure to a recognizable and extreme stressor; in contrast, borderline personality disorder consists of the early-onset, enduring personality traits described elsewhere in this guideline.

Although borderline personality disorder may be comorbid with dissociative identity disorder, the latter (unlike borderline personality disorder) is characterized by the presence of two or more distinct identities or personality states that alternate, manifesting different patterns of behavior.

Borderline personality disorder is the most common personality disorder in clinical settings. It is present in 10% of individuals seen in outpatient mental health clinics, 15%–20% of psychiatric inpatients, and 30%–60% of clinical populations with a personality disorder. It occurs in an estimated 2% of the general population (1, 136).

Borderline personality disorder is diagnosed predominantly in women, with an estimated gender ratio of 3:1. The disorder is present in cultures around the world. It is approximately five times more common among first-degree biological relatives of those with the disorder than in the general population. There is also a greater familial risk for substance-related disorders, antisocial personality disorder, and mood disorders.

Long-term follow-up studies of treated patients with borderline personality disorder indicate that the course is variable. Early adulthood is often characterized by chronic instability, with episodes of serious affective and impulsive dyscontrol and high levels of use of health and mental health resources. Later in life, a majority of individuals attain greater stability in social and occupational functioning.

In the largest follow-up study to date (137), about one-third of patients with borderline personality disorder had recovered by the follow-up evaluation, having solidified their identity during the intervening years and having replaced their tendency toward self-damaging acts, inordinate anger, and stormy relationships with more mature and more modulated behavior patterns. Longitudinal studies of hospitalized patients with borderline personality disorder indicate that even though they may gradually attain functional roles 10–15 years after admission to psychiatric facilities, only about one-half of the women and one-quarter of the men will have attained enduring success in intimacy (as indicated by marriage or long-term sexual partnership) (137). One-half to three-quarters will have by that time achieved stable full-time employment. These studies concentrated on patients with borderline personality disorder from middle-class or upper-middle-class families. Patients with borderline personality disorder from backgrounds of poverty have substantially lower success rates in the spheres of intimacy and work. Despite these somewhat favorable outcomes, the suicide rate among patients with borderline personality disorder is high—approximately 9%. The risk of suicide appears highest in the young-adult years.