What are the similarities and differences between borderline personality disorder and bipolar disorder?

The distinction between bipolar disorder and borderline personality disorder is one of the most hotly studied and debated issues today in terms of research and clinical care.  The greatest debate occurs regarding the bipolar spectrum disorders, although bipolar I disorder shares some elements with borderline personality disorder as well.  The two extreme arguments range from negating bipolar II/bipolar NOS disorders that overlap with borderline personality disorder to negating borderline personality disorder, with the arguments from most clinicians and researchers falling somewhere in between.  Although bipolar II is a relatively new disorder and was not operationalized until the publication of DSM-IV in 1994, this debate has been ongoing since the criteria for borderline personality disorder were first established in 1980 with the publications of DSM-III.  Borderline personality disorder is characterized by a pervasive pattern of instability of interpersonal relationships, self-image, and affects, as well as marked impulsivity.  Symptoms begin by early adulthood and include:

• Frantic efforts to avoid real or imagined abandonment
• Extremes of idealization and devaluation of interpersonal relationships
• Markedly and persistent unstable self-image or sense of self
• Impulsivity in at least two areas that are potentially self-damagin (e.g., spending, sex, substance abuse, reckless driving, binge eating)
• Recurrent suicidal behavior, gestures or threats, or self-mutilating behavior
• Affective instability due to a marked reactivity of mood (e.g., intense episodic dysphoria, irritability, or anxiety)
• Chronic feelings of emptiness
• Inappropriate, intense anger or difficulty controling anger (e.g., frequent displays of temper, constant anger, recurrent physical fights)
• Transient, stress-related paranoia or severe dissociative symptoms

The symptoms noted in bold are similar to those that occur during a hypomanic or manic episode, which is where the overlap in diagnosis can occur.  The other criteria, however, are more distinct and characterize or are associated with the long-standing troubled interpersonal relationships.

The history of the term borderline personality is an interesting one.  Originally the term was used to describe patients whose symptoms traversed the boder between "neurosis" and psychosis.  The individuals were considered "pseudoneurotic schizophrenecs" because their general ability to adapt was profoundly impaired although superficially they appeared unremarkable.  Borderline patients can in fact become transiently psychotic in the midst of one of their rages, but later such patients were characterized instead as having emotionally unstable personalities.  In 1975 the psychiatrist Otto Kernberg conceptualized borderline personality disorder as a diagnosis associated with particular primitive defense mechanisms, of which splitting was one.  The criterion regarding patients tendency to overidealize or devalue another person is an example of splitting, in which they have difficulty integrating the good and bad in people and thus "split" the person into either all good or all bad.  Personality traits are thought to be different from symptoms associated with mood disorders in that they are a reflection of enduring patterns of perceiving, relating to, and thinking about the environment relative to oneself and are exhibited in a wide range of contexts.  These traits are generally first recognized in adolescence and endure throughout adult life.

A recent study examining the affective instability common to both borderline personality and bipolar II disorder patients found clear differences between the types of affects associated with the two disorders.  Borderline personality disorder was associated with greater mood lability in terms of anger, anxiety, and depression/anxiety oscillation, while bipolar II disorder was associated with greater mood lability in terms of depression, elation, and depression/elation oscillation.  In fact, the study also showed that labile anger alone was sufficient to predict (with 72% accuracy) the diagnosis of borderline personality disorder versus another personality disorder.  This finding is surprising, given the fact that bipolar II disorder is considered to be more often associated with irritability than bipolar I disorder, which is more associated with euphoria or elation.  Additionally, another clear distinction exists in the underlying sense of self between the two disorders.  Patients with borderline personality disorder suffer from feelings of emptiness with strong fears of abandonment--feelings that are always present even when the mood is generally stable.  Bipolar patients, on the other hand, have a generally stable sense of self when their moods are stabilized.

Leaving aside the validity of such a reconceptualization of the two diagnostic categories, whether or not there is utility to this approach is the more important question.  After all, the ultimate goal of establishing diagnostic accuracy is for the purposes of treatment.  With the newer antipsychotic medications that are now approved for bipolar disorder, the utilization of pharmacological interventions for treating a condition that was once thought to be solely amenable to long-term psychotherapy offers new hope for these patients.  Keep in mind, however, that such medications are neither diagnostic nor symptom specific and therefore a positive response does not ensure diagnostic validity.  Increasing research in this area has demonstrated some modest success in stabilization of borderline personality symptoms with combinations of mood stabilizers and/or antipsychotics.  The emphasis on psychotherapy, howver, continues to be the primary mode of treatment for patients with borderline personality disorder.  The most utilized and validated psychotherapeutic techniques for borderline personality disorder is dialectical behavior therapy, designed and studied by Dr. Marsha Linehan.  This technique focuses on behaviors and less so on feelings except with respect to how they link directly to self-injury.  Studies in Europe have demonstrated a decrease in both suicidal and self-destructive behaviors, though effect on mood is less certain.