The existential crisis of bipolar II disorder

Abstract

The issue of categorical vs. dimensional classification of bipolar disorder continues to generate controversy as it has for generations. Despite the evidence that no psychiatric disorder has discrete boundaries separating pathological and nonpathological states, and within a disorder, no clear differences separate subtypes-which would suggest a more dimensional approach-there are valid reasons to continue with our current categorical system, which distinguishes bipolar I from bipolar II disorder. Complicating the issue, a number of interested constituencies, including patients and their families, clinicians, scientists/researchers, and governmental agencies and insurance companies have different interests and needs in this controversy. This paper reviews both the advantages and disadvantages of continuing the bipolar I/bipolar II split vs. redefining bipolar disorder as one unified diagnosis. Even with one unified diagnosis, other aspects of psychopathology can be used to further describe and classify the disorder. These include both predominant polarity and categorizing symptoms by ACE-activity, cognition and energy. As a field, we must decide whether changing our current classification before we have a defining biology and genetic profile of bipolar disorder is worth the disruption in our current diagnostic system.

Keywords: Bipolar I; Bipolar II; Diagnosis; Nomenclature.

Fig. 1

ACE Model of mania. This schematic shows how manic drive, perhaps through differential action on different symptomatic domains can create a seemingly separate phenotype when in fact the difference in manifestation is largely because of the inherent properties of different neurocognitive schema and neural systems within the brain. In florid mania, manic drive (shown in yellow) is so extreme that irrespective of the inherent rigidity of various domains, they are all extended (akin to elastic bands) to the same extent. And so, activity, cognition and emotion are all impacted equally and symptoms from each of these domains are evident. However, when manic drive is more modest, those domains that are inherently more pliant are impacted first and hence why there is separation between emotion, cognition and activity. Emotion, by its very nature is more malleable and variable, whereas cognition succumbs more slowly, and activity is the most hard-wired and therefore requires significant manic drive before it is impacted. The figure also shows that lesser degrees of variation and more subtle changes lead to a more mixed presentation in which features of both mania and depression exist alongside each other, by virtue of belonging to independent domains (ACE). This schematic then explains how ‘bipolar II’ and other putative subtypes could perhaps be created and yet have the same underlying mechanisms and therefore, in essence, remain the same illness