COMMENTARY

8 Controversies in Bipolar Disorder Addressed

Nassir Ghaemi, MD, MPH; Stephen M. Strakowski, MD

Disclosures

June 30, 2016

Controversy 5: BD or Borderline?

How can BD be distinguished from borderline personality disorder?

Dr Ghaemi: Not by using the Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5), in my view. Most people focus on mood lability, which is a useless criterion because it is shared by both conditions. So too is the case with sexual impulsivity and unstable relationships. To differentiate conditions, one should focus on what is different between them, not what is the same.

The problem with the DSM is that it mostly lists only symptom criteria, but it doesn't use other diagnostic validators in its criteria. Other validators of importance are course of illness and genetics.

BD is highly genetic (about 80%-90% heritability in meta-analyzed data); borderline personality, according to meta-analyzed data, is more mildly so (about 50% heritability in meta-analyzed data). They have different courses: Borderline personality was conceived as occurring in persons with childhood trauma that was often sexual, usually repetitive, and associated with repeated parasuicidal self-harm. BD has none of the above features but begins on average at age 19 years, and in about one half of persons, there is normal functioning between episodes. Thus, I would focus on the course of illness and genetic criteria to differentiate these conditions.

Dr Strakowski: Dr Ghaemi hits on the two key points that I use when making this distinction. The first is that BD is highly heritable, so a lack of any family history of psychiatric illness makes the diagnosis suspect (and a borderline personality disorder perhaps more likely).

The second is that borderline personality disorder, as defined as a "personality disorder," is not really established until the late teens/early 20s and then is essentially persistent over time. In contrast, BD is episodic, with improved function during euthymic periods; this distinction is the most useful from a diagnostic perspective.

The two conditions are not mutually exclusive, however, so both may occur. My general rule of thumb when uncertain is to err on the side of broader treatment options and better prognosis (ie, a diagnosis of BD) to make treatment decisions and while accumulating additional information.

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