Bipolar II Disorder: Current Issues in Diagnosis and Management

August 2006, Vol. XXIII, No. 9

According to DSM-IV,^1, diagnosis of bipolar disorder (BP) II requires the presence of major depressive and hypomanic episodes. DSM-IV further characterizes hypomania as requiring (a) periods of elevated or irritable mood (mood changes), which must always be present and must last at least 4 days, different from the usual mood; (b) 3 of the following 8 symptoms if mood is elevated, 4 if mood is irritable: inflated self-esteem, decreased need for sleep, more talkativeness, racing thoughts, distractibility, increased goaldirected activity, psychomotor agitation, and excessive involvement in risky activities; (c) change in functioning; (d) observable mood and functioning change; (e) no marked impairment of functioning, no psychotic symptoms; and (f) symptoms must not be caused by substances, drugs (including antidepressants), or medical disorders.

This article will focus on 3 issues of current concern: diagnostic criteria for hypomania, diagnosis of mixed depression, and management of mixed depression.

Prevalence of BP II

A recent series of studies has found that BP II is much more common than the 0.5% community prevalence reported by DSM-IV: the current estimate of community prevalence is about 5%.^2-4 However, clinical studies in different settings have found a much higher prevalence of BP II among depressed outpatients, reporting an equal number with major depressive disorder (MDD) in a ratio of 1:1.^5-13

In comparison to previous studies, ^4,8,10-15 the much higher prevalence of BP II found in these studies is related to the following methodologic advances:

• Use of semistructured interviews by trained clinicians.
• A minimum duration of hypomania of 2 or more days.
• Bypassing the stem question of DSM-IV to assess the history of hypomania.
• Focusing the probing for history of hypomania on overactivity.

The use of fully structured interviews by lay interviewers, which used yes/no questions and did not provide for clinical evaluation, often led to underdiagnosis of BP II or misdiagnosis of BP II as MDD. The use of semistructured interviews by trained clinicians provides a clearer diagnostic perspective and consequently, a smaller margin of error.

Using the criteria of a minimum duration of hypomania of 2 or more days rather than the DSM-IV 4-day cutoff may increase accurate diagnosis. Unlike the 4-day cutoff, the 2-day cutoff is based on data that show no difference on bipolar measures such as family history, age at onset, and number of recurrences. When DSM-IV criteria are strictly followed, BP II is often (at least 30% of the time) misdiagnosed as MDD.

Because the DSM-IV stem question requires remembering periods of elevated or irritable mood, the response to this question by patients with BP II is frequently “no,” since these periods may be seen as normal mood fluctuations. If the wording of the question includes “much more than usual,” this may be perceived as a sign of a severe mental disorder, and is often denied. Bypassing the stem question of DSM-IV to assess the history of hypomania can provide a more accurate diagnosis.

Overactivity (increased goal-directed activities) is an observable behavior, easier to remember than the mood state required by DSM-IV. During the initial interview, relatives and friends can report on mood changes that are more easily recalled after remembering a period of overactivity. Overactivity has been found to be the core feature of hypomania, and it can have at least the same priority as mood changes for the diagnosis of BP II.^4,11,13,16

Factor analysis studies and clinical studies have supported the upgrading of overactivity. Factor analysis studies have shown that “activation” is the core feature of hypomania. Many DSM-IV symptoms of hypomania (7 of 9) could be considered to be the result of an activation/excitement state of the brain: increased goal-directed activity, psychomotor agitation, decreased need for sleep, more talkativeness, racing thoughts, distractibility, and excessive involvement in risky activities.

In 1913, Kraepelin¹⁷ described 3 basic domains of mania/hypomania and depression: excitement or inhibition of mood, thinking, and behavior. He did not set any priority among them, but stated that “increased busyness,” ie, overactivity, was “the most striking feature” of hypomania. His predecessors, Falret (1854) and Hecker (1898) noted the diagnostic utility of behavioral activation for the diagnosis of disorders similar to BP II, ie, “cyclothymia” and “circular insanity.”^18,19 Actually, in Kraepelin’s view, there could be a manic state even without an elevated mood, as in the mixed state “depressive or anxious mania.” According to DSM-IV, elevated mood is the prototypical symptom of hypomania. This may mislead clinicians into believing that the basic feature of hypomania is elevated mood and that the other symptoms are secondary and less important.

The major depressive episodes of BP II, and not uncommonly those of MDD, may have concurrent hypomanic symptoms but cannot include elevated mood and the related inflated self-esteem. These mixed depressions thus become “missed” depressions. Mixed depression misdiagnosis impacts negatively on the treatment of depression. Clinical studies have shown that BP II diagnosed by setting overactivity, and not mood changes, as the priority symptom of hypomania is similar on diagnostic measures to DSM-IV BP II, which requires mood changes for the diagnosis of hypomania. Diagnosing hypomania by requiring overactivity does not lead to overdiagnosis of BP II, and most DSM-IV BP II (approximately 80%) is included.

The Structured Clinical Interview for DSM-IV (SCID)²⁰ has the disadvantage of having the stem question for hypomania based on mood changes, if the response is negative, assessment must move to nonbipolar disorders. Another important disadvantage of the SCID is that it does not assess hypomania/hypomanic symptoms in a major depressive episode, leading to missing mixed depressions, especially in outpatients.

Two recent studies have reported on mixed hypomania, which is a combination of hypomania and depressive symptoms or a major depressive episode. ^21,22 This diagnosis also will be missed by the SCID. Patients with BP II may not seek treatment for hypomania, because it is frequently seen as a period of improved functioning. Impairment in hypomania, when it occurs, is mild, and is seen more often by relatives and friends than by patients with hypomanic BP II.

Basic data support distinction between BP I and BP II

The basic data supporting a distinction between BP I and BP II^23,24 are presented in the Table. In comparison to BP I, there are many fewer studies of BP II and there is little evidence to support the treatment guidelines. Compared with BP I, patients with BP II are more prone to episodes of depression, higher Axis I comorbidity (especially panic disorder), a higher suicide risk, and a high incidence of substance abuse.^9,25-28