Major Depressive Disorder With Subthreshold Bipolarity: Exploring and Managing New Diagnoses
The article by Angst and colleagues in this issue (1) proposes an additional disorder within the spectrum of bipolar disorders, involving people who have major depressive disorder and subthreshold hypomania symptoms. This condition differs from major depression in having more familial bipolar disorder, a younger age at onset, more severe symptoms, higher rates of comorbidity, and more depressive episodes. However, lifetime and 12-month histories of treatment as well as level of disability do not differ from those of major depression. Compared with patients who have bipolar I and II disorders, this new group manifests less severe manic symptoms, less disability, and less treatment (both lifetime and 12-month).
This epidemiological study, based on data from the National Comorbidity Survey Replication, was carefully done, with a large sample, using state-of-the-art sampling methods and data collection instruments. The authors findings support other surveys as well as clinical descriptions. From a Linnean standpoint, the validity of this new disorder (perhaps a “bipolar III” disorder) holds up well: it bears greater genetic loading, pathology, and morbid prognosis than does major depression, yet less morbidity and treatment than bipolar I and II disorders.
Clinicians might accept this new diagnosis for its ability to set a more accurate prognosis than previously possible. However, to truly welcome a new entity to their daily practice, clinicians may want more information, such as the following:
| •. | How should one treat this condition to realize an optimal outcome? Should these patients receive mood stabilizers, and if so, which ones? Are antipsychotic medications (along with their problems) warranted if mood stabilizers fail to relieve the symptoms? | ||||
| •. | Will some of these patients progress over time to bipolar I or II disorder? With age, will some settle into recurrences of major depression? | ||||
| •. | In what ways does treatment make a difference? Does it relieve disability or reduce the prevalence of comorbidity, or both? | ||||
| •. | Do patients with substance use disorders or other behavioral comorbidity require additional or different treatment compared to those without such disorders? | ||||
| •. | What is the effficacy of psychotherapy in this disorder? | ||||
| •. | Given the relatively high prevalence of this disorder (lifetime prevalence, 6.7%; 12-month prevalence, 2.2%), what are the economic implications of this disorder? | ||||
Cross-sectional epidemiological studies alone cannot provide this critical information. Controlled treatment studies, long-term prospective studies, and cost- effectiveness studies are needed. Although much work remains to be done, we owe a great debt to Angst and colleagues for bringing us this far.
Implications.
We are in a period when new technologies and more refined studies are identifying ever more new disorders. For example, a recent report suggests that major depression in the presence of “hyperthymic temperament” may comprise a distinct bipolar IV condition (2). Some psychiatrists are growing alarmed at this apparent propensity to create ever more diagnoses. Will each new edition of DSM produce a geometric increase in the number of psychiatric disorders? Will an exponential growth in diagnoses lead to greater confusion or to greater clarity in our clinical work? Will we become overwhelmed with a focus on subsyndromal “trees” while rendering ourselves incapable of comprehending the overall “forest”?
Several countervailing trends offer promise in balancing the dizzying array of new disorders, subdisorders, and sub-subdisorders. These trends (not in any order of implied significance) include the following:
| •. | An emphasis on treatment equal to the emphasis on pathology, genetics, or course of illness may cordon off potential new disorders from clinical application until their clinical utility can be assessed. Since treatments for many differing disorders involve the same or similar modalities (e.g., cognitive-behavioral therapy, antidepressants), this approach may facilitate linkages among disorders (3). As an example, substance abuse and dependence could telescope down to a single substance use disorder because treatment and prognoses fail to distinguish the two subgroups despite their differences along genetic, pathological, and other characteristics. | ||||
| •. | The focus on “spectrum disorders” may reduce the number of overarching categories despite the fact that some subcategories are multiplying. For example, mood disorders may range from bipolar I through dysthymia through adjustment reaction with mood symptoms. Schizophrenia spectrum, impulsive behavioral spectrum, certain neurotransmitter spectra, and other spectra are being discussed. This approach may help clinicians master the complexity of new findings while providing an understandable paradigm to the general population. It might persuade the population, our social institutions, and our profession of the importance of discerning ways to contain any given “spectrum disorder” at its least disabling and least morbid stage. | ||||
| •. | A growing emphasis on “longitudinal comorbidity” is also informing us about what disorders are apt to ensue in the wake of an earlier disorder. This provides us with additional opportunities to prevent the subsequent disorders and to learn the progenitors of disorders (since the parties to these sequences often follow a patterned rather than a random progression). An example is the subsequent development of mood disorder in those who have had an anxiety disorder (4)-an example of internalizing disorders recurring over time in altered form. Primary care clinicians as well as mental health professionals need lucid models to understand longitudinal comorbidity in order to skillfully monitor patients over time and implement prompt interventions as needed (5). | ||||
| •. | The resurrection of internalizing-versus-externalizing psychiatric disorder, after almost a half century of relative neglect, may bring some order to the field. Although these moieties were originally employed for the study of children, research in adults has shown nonrandom co-occurrence of internalizing disorders with one another and of externalizing disorders with one another. Grouping mood and anxiety disorders into a single internalizing category has advanced the search for causation, exemplified by the combining of adverse childhood events with internalizing disorder to produce substance use disorder (6). Likewise, grouping externalizing disorders has increased our knowledge, as shown by the interaction of genetic and environmental factors to produce diverse externalizing disorders (7). | ||||
| •. | As clinicians come to better understand diagnoses, they will be able to educate patients and families more successfully than in the past. This will serve the large number of suffering people whose need for care goes unmet (8). Although treatment seeking by now-untreated legions of people could overwhelm resources (9), the development of computer-based or computer-augmented therapy may increase treatment success while reducing cost (10). | ||||
We are entering an exciting period of change in psychiatric nosology. A tension exists between, on the one hand, the potential for a psychiatric Tower of Babel, in which categories proliferate so greatly as to undermine our ability to apply them reliably, and on the other hand, the potential of these new categories to inform and improve our care of people who are distraught, disabled, demoralized, or even destroyed by their conditions. We can—and I am confident that we will—fi nd sensible means of integrating these innovations into our daily work.
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2. : Hyperthymic temperament may protect against suicidal ideation. J Affect Disord (Epub ahead of print, May 11, 2010)Google Scholar
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