Diagnosis of Bipolar Disorders: Focus on Bipolar Disorder I and Bipolar Disorder II

Charles L. Bowden, MD

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Diagnosis of Bipolar Disorders

Bipolar disorders recognized in the DSM-IV include bipolar I, bipolar II, cyclothymic disorder, and bipolar disorder not otherwise specified. The diagnostic and associated features of these entities are listed in Table 1 . A diagnosis of any of these bipolar disorders requires first that the presence of a mood disturbance has been ascertained, and that other causes of the symptoms observed have been ruled out. Most notable among conditions that can confound diagnosis by presenting similar symptoms are mood disorders due to a general medical condition (eg, multiple sclerosis, hypothyroidism) ( Table 2 ) or substance abuse ( Table 3 ). These can be diagnosed as separate entities distinct from bipolar disorders (referred to, respectively, as "mood disorder due to a general medical condition" and "substance-induced mood disorder"), which can, in most cases, be distinguished by patient history and clinical or physical findings. If these other causes are dismissed, diagnosis of a bipolar disorder is next contingent on specifying the duration, quality, and degree of mania-like symptoms. Although not part of the DSM-IV, Akiskal has suggested that the inclusion of a positive family history be a part of diagnosis.[3] The inclusion of this criterion may be particularly useful in patients with subthreshold disease and mixed states.

Bipolar I disorder is diagnosed when there is a history or current evidence of a "pure manic" or "mixed" episode. A pure manic episode is an abnormally and persistently elevated, expansive, or irritable mood that is accompanied by at least 3 (or 4, if the primary mood is irritable) other symptoms ( Table 4 ). Mixed episodes have features of mania intermixed with symptoms of a major depressive episode that cause significant impairment of functioning and/or require hospitalization. Periods between a manic or a mixed episode may be characterized by major depression with features similar to those seen in unipolar depressive episodes or, instead, by relative euthymia. Bipolar II disorder is diagnosed when episodes of excitement of at least 4 days duration have been or are present, but which are less dramatic than those for mania and do not require hospitalization. A history or current symptoms of major depression must also characterize the patient diagnosed with bipolar II. Periods of hypomania that have not lasted 4 days typically warrant a diagnosis of bipolar not otherwise specified. This diagnosis also is appropriate for patients who have hypomanic symptoms but insufficient depressive symptoms.[1] And, finally, cyclothymia is the diagnosis of cyclic manic and depressive symptoms that are not of sufficient magnitude or duration to warrant a diagnosis of bipolar I or bipolar II, but have occurred over at least a 2-year period with symptom-free intervals of less than 2 months ( Table 5 ).

Currently accepted (DSM-IV) specifiers or course modifiers that further describe the natural history of a diagnosed bipolar disorder include a variety of distinctive symptomatic or temporal features. These include the degree of severity (or remission) of the current or most recent manic, mixed, or major depressive episode; existence of psychotic, melancholic, or atypical features; association with a recent childbirth; and others. Among these, the condition of "rapid cycling" has been receiving substantial interest, with the recognition that 10% to 15% of patients with diagnosed bipolar I or bipolar II disorder have cycle lengths of such short duration that they suffer 4 or more cycles per year (vs the more typical temporal pattern of 4 episodes in 10 years).[4,5,6] Patient characteristics that are associated with rapid cycling include female gender and hypothyroidism that is independent of its greater overall prevalence in females and is without evidence of familial association.[4,5,6] Whether there is a long-term morbidity risk associated with rapid cycling, as is seen in the short term, remains to be fully evaluated. This evaluation will be complicated by a likelihood that there is a spectrum of conditions that falls under the rubric of "rapid cycling."[7]

The distinctive features of a manic or mixed episode make the designation of a bipolar I subtype vs bipolar II subtype fairly clear, although the relative degree of symptomatology (milder manifestations in bipolar II) is an admittedly subjective component to the distinction. Beyond severity of symptoms, however, there is evidence that there are underlying genetic, biologic, and clinical differences between bipolar I and bipolar II disorders.[8] For example, the incidence of episodes has been found to be greater in patients categorized as having bipolar II disorder compared with bipolar I, although their rates of hospitalization and presence of psychotic symptoms were found to be significantly lower.[9] There also is evidence of different genetic linkage patterns associated with these 2 bipolar subtypes.[10]

The utility of a bipolar I and bipolar II designation will emerge as studies compare patients identified on the assumption that they represent clinically relevant subtypes of bipolar disorders. Less far along is the incorporation into our diagnoses of categories of other manic-like states of differing magnitude, duration, or frequency. Such conditions clearly exist and justify the concept of a bipolar spectrum, and indeed of a continuum between bipolar and unipolar disorders, for which the possibility of chiseling out additional distinctive disorders is being evaluated.[3] The designation of bipolar II not only has provided an acknowledgment that there can be a distinction between euthymia and hypomania for patients with depressive episodes (and that the latter may not become apparent until good response to antidepressants is achieved), but also has placed a condition of a 4-day minimum to the duration of hypomanic-like states to distinguish bipolar II from cyclothymic disorder. In reality, this may be a clinically arbitrary limit. Additionally, in some patients, major depression may alternate with cyclothymic episodes (shorter than 4-day duration of manic-like symptoms alternating with depressive-like symptoms) rather than with hyperthymic episodes. Further, the designation of bipolar III disorder has been suggested for those patients for whom a hypothymic state appears to be the baseline from which their major depressive episodes emerge.[3] Surely, further delineations will be needed within the remaining cyclothymic or not otherwise specified bipolar rubrics, as our knowledge of mood disorders becomes more sophisticated.

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