How are Bipolar and Borderline Personality Disorder Similar?
The primary reason that some experts have proposed that BPD and bipolar disorder may be related is that they share the common feature of mood instability. Bipolar disorder is associated with mood shifts from depression to mania (a mood characterized by elation, decreased need for sleep, and an increase in activity) or hypomania (which is similar to mania but less severe). BPD is also associated with mood changes (sometimes called "emotion dysregulation" or affective instability). People with BPD can frequently change from feeling fine to feeling extremely distressed in a matter of minutes. Impulsive behavior is also frequently experienced both by people with bipolar disorder and by people with BPD.
How are Bipolar and Borderline Personality Disorder Different?
What is the difference between BPD and bipolar disorder, then? Some major components separate the two. While the disorders are both characterized by mood changes, the quality of the mood changes can be very different. In BPD, mood changes are often more short-lived -- they may last for a few hours at a time. In contrast, mood changes in bipolar disorder tend to last for days or even weeks. Also, mood shifts in BPD are usually in reaction to an environmental stressor (such as an argument with a loved one), whereas mood shifts in bipolar disorder may occur out-of-the-blue. Finally, the mood shifts typical of BPD rarely involve elation -- usually the shift is from feeling upset to feeling "OK," not from feeling bad to feeling a high or elevated mood, which is more typical of bipolar disorder.
Are Bipolar and Borderline Personality Disorder Related?
Although it is not yet clear-cut, research has not found a strong relationship between BPD and bipolar disorder. There is some evidence that people with BPD are diagnosed with bipolar disorder at higher rates than individuals with other personality disorders. One study found that about 20% of individuals with BPD are also diagnosed with bipolar disorder, whereas only about 10% of people with with other personality disorders are also diagnosed with bipolar disorder. This could mean there is some relationship between BPD and bipolar, but it could also be attributed to imprecision in diagnosis, or in the individuals making the diagnosis.
Bipolar and Borderline Personality Disorder: The Bottom Line
So far, there is not enough research to suggest that BPD and bipolar disorder are related. Although there are definitely some shared features, there are also some marked differences between BPD and bipolar disorder. Also, the co-occurrence of BPD and bipolar disorder is not large enough to suggest that the two disorders are related. However, more research is needed on this topic. It may be that future research, for example on the genetic and biological causes of BPD and bipolar disorder, may reveal some undiscovered elationships between the two conditions.
American Psychiatric Association. Diagnostic and statistical manual of mental disorders, 4th ed, text revision. Washington, DC, Author, 2000.
Gunderson JG, Weingberg I, Daversa MT, Kueppenbender KD, et al. "Descriptive and Longitudinal Observations on the Relationship of Borderline Personality Disorder and Bipolar Disorder." American Journal of Psychiatry, 163:1173-1179, 2006.
Paris, J. "Borderline or Bipolar? Distinguishing Borderline Personality Disorder from Bipolar Spectrum Disorders." Harvard Review of Psychiatry, 12:140-145, 2004.