Special articleThe bipolar spectrum: a clinical reality in search of diagnostic criteria and an assessment methodology
Introduction
Both classical (Kraepelin, 1921) and contemporary (Akiskal, 1983, Goodwin and Jamison, 1990) observations support the thesis that bipolarity is expressed along a severity spectrum. The progress of clinical therapeutics over the past two decades has expanded the boundary of bipolar disorder and its varied phenomenology and epidemiology. Within the same period there has been considerable interest in identifying subclinical and/or subthreshold expressions of this disorder (Akiskal, 1983, Akiskal and Mallya, 1987, Akiskal, 1996). However, these subtle forms of bipolar disorder still are overlooked both in clinical settings and epidemiological studies. Subthreshold mania has been described using a myriad of clinical labels including soft, subtle, partial, incomplete, mild, atypical, subliminal and attenuated. We believe that none of the descriptions provided to date provides a complete definition encompassing the full range of characteristics of subthreshold mania. We also believe the terms themselves are somewhat inaccurate and potentially misleading. For example, the term `soft' (Akiskal and Mallya, 1987), could suggest inadvertently a lack of solid, clear form of symptomatology, or the term `subtle' might refer to a fine and elusive symptomatology that can be difficult to recognize.
In this paper, we use the term `subthreshold bipolar spectrum' for those patients who show features of bipolar disorder, but whose symptoms are not severe enough to fulfil the diagnostic criteria of ICD-10 (WHO, 1992) and DSM-IV (APA, 1994) for bipolar disorder. The entire bipolar spectrum encompasses conditions with typical DSM-IV bipolar symptoms that are clinically significant and almost meet the criteria of a bipolar disorder subtype (Bipolar NOS according to the DSM-IV), as well as those that meet symptom criteria but are considered `subclinical' in that they do not cause impairment to the individual and/or do not require treatment. However, bipolar spectrum may also be diagnosed if there are atypical symptoms or personality traits not found in the criteria section of DSM-IV or ICD-10, but indicative of a bipolar diathesis.
We believe that the accuracy of diagnosis of bipolar disorder could be improved through the introduction of a refined procedure for the detection and evaluation of a broader range of symptoms relevant to mania. For example, identification of different forms of manic symptoms including psychotic or confused/stuporous symptoms and subthreshold symptoms could be helpful in making a diagnosis (Akiskal, 1983Akiskal, 1996Angst, 1995).
This paper argues that systematic study of the spectrum of bipolar symptoms using a structured clinical interview will be relevant to the diagnosis, treatment and epidemiology of bipolar disorder. Indeed, as Angst (1995)has recently argued, subthreshold syndromes frequently demand treatment and one should not underestimate the severity of their social impact and treatment needs.
Section snippets
The need to better delineate the manic/hypomanic component of bipolar disorder
The DSM-IV™ criteria for a manic episode are fairly limited, perhaps in part because of the stigma associated with a diagnosis of manic-depressive illness. Recently, there has been interest in subthreshold depression and anxiety (Judd et al., 1994, Olfson et al., 1996, Akiskal et al., 1997), but relatively less attention has been given to subthreshold mania. Under-diagnosis of subthreshold forms of mania may lengthen the time to recognition of illness and this could delay treatment and worsen
Bipolar II disorder
Although hypomanic manifestations received extensive coverage in Kraepelin's treatise on manic-depressive insanity (Kraepelin, 1921), bipolar II as a specified bipolar subtype was first described by Dunner et al. (1976)at NIMH.
BP II disorder, as currently defined in the DSM-lV™, shows diagnostic stability (Angst, 1986, Coryell et al., 1987, Coryell, 1996), a greater risk of the same disorder among the relatives of an affected subject (Coryell et al., 1984, Endicott et al., 1985), a high
Bipolar III disorder
Subthreshold bipolar manifestations were characterized in a sample of 687 patients selected for the presence of an index episode of major depression in a collaborative study with the Universities of Pisa and Tennessee (Musetti et al., 1989, Cassano et al., 1992b). Patients whose UP depression arose from a `hyperthymic' temperament (UP-HT), were compared with groups of patients with BP I, BP II and `pure' UP. We found UP-HT subjects were similar to the bipolar patients on some characteristics,
Mixed presentations of subthreshold bipolar spectrum
Kraepelin (1921)first described mixed states as the coexistence of depressive and manic symptoms. Since his classic description, mixed states have not received extensive research evaluation. The clinical manifestations of mixed states are polymorphic (Dell'Osso et al., 1991) and include psychotic forms, with incongruous delusions and hallucinations (Akiskal and Puzantian, 1979, Dell'Osso et al., 1993, Perugi et al., 1997) as well as milder and sub-clinical conditions (Akiskal and Mallya, 1987),
SCI-MOODS: A structured clinical interview for the mood spectrum
Although our spectrum concept in no way rejects the DSM™ or ICD™ affective categories, it does provide a broader range of symptoms allowing for the possibility that there is not a clear distinction between different DSM mood categories. We see our conceptualization similar to Kraepelin (1921)when he created the rubric of `manic-depressive insanity' that for him spanned from the mildest affective to the most extreme psychotic. By including altered mood and mood related features in one spectrum
Concluding remarks
Patients affected by brief-recurrent or chronic subthreshold bipolar syndromes should not be considered as “a group of subjects where symptoms failed to meet the threshold for a diagnosis” (Angst, 1997). The current diagnostic manuals (DSM-IV™ and ICD-10™) tend to exclude all but `threshold psychiatry', thus reflecting the trends in some countries to limit psychiatry (both clinical intervention and research) to established diagnostic groups. The current state of these manuals also reflects the
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