Duration criteria
Clinicians and researchers have debated the minimum duration criteria for identifying manic or hypomanic episodes, and the extent to which suspected hypomanic periods of short duration constitute distinct illness phases. Although DSM-IV-TR designates 4 days as a minimum time for classifying an episode of hypomania, empirical studies suggest that mood symptoms lasting as few as 2 days may comprise a valid and reliably distinct entity relevant to RC.5 More limited data (mainly case observations) identify “affective oscillations” and “mood shifts” occurring faster than once per 24 hours in BD patients without comorbid personality disorders.6 Phenomenologic studies that have focused on 24- to 48-hour switch cycles have described new-onset URC arising spontaneously or following closed head injuries.7 In children and younger adolescents, reports have identified long index manic episodes (mean durations as long as 80 weeks)8 that involve continual (ultradian) mood cycling in as many as 80% of cases.9
Is URC a valid construct?
A central controversy surrounding the validity and meaningfulness of URC as a BD subtype involves its sole focus on mood variation rather than the fuller constellation of associated signs and symptoms that define episodes of mania/hypomania or depression. Abrupt, sudden, drastic, or dramatic mood shifts from one moment to the next are nowhere to be found in the DSM-IV-TR definition of BD, and the construct of mood lability or affective instability is neither a cardinal nor defining element of BD. Although individuals with BD I or bipolar II disorder (BD II) may have periods of affective lability, rapid shifts in mood are neither necessary nor sufficient for a BD diagnosis, and may indicate other types of psychopathology when affective instability occurs in the absence of a history of discernible manic or hypomanic episodes.
Studies by our group10 and others11 have shown that overattention to mood variation without considering associated cognitive, speech-language, chronobiologic, and motor signs of mania/hypomania accounts for substantial overdiagnosis of BD in patients with non-specific mood disturbances, particularly in those with active substance abuse or borderline personality disorder (BPD). Whereas the construct of RC BD attempts to account for changes in energy and psychomotor function as part of recurrent syndromes of mania/hypomania, existing literature on URC does not. Assessing mood changes in <24 hours also precludes assessing associated phenomena that occur over longer periods, such as changes in the sleep-wake cycle.
A rigorous, systematic approach to differential diagnosis for patients with affective instability is essential.
Borderline personality disorder
A common diagnostic debate regarding URC involves how to differentiate it from the chronic mood instability and reactivity inherent to BPD. Although some authors have suggested that RC BD and affective instability in BPD may be the same entity,12 others object to unifying the 2 conditions without considering their phenomenologic and other clinical differences. For example, affective instability arising from borderline character organization is thought to reflect a patient’s impaired capacity to self-regulate his or her internal state and emotional responses to interpersonal and other environmental stresses, or difficulty managing impulses. By contrast, manic or depressive phases of BD tend not to be “triggered” by interpersonal conflicts or frustrations. Furthermore, reframing intense mood reactions to the environment as bipolar variants carries several pitfalls: doing so wrongly accords patients a passive role in their reactions to life events, inaccurately reinforces a sense of victimization in response to stress, and diverts inquiry away from a patient’s active role in life decisions and circumstances that may be unsatisfying, self-defeating, or volatile.
Two key considerations may be helpful in discriminating rapid mood changes in BD vs BPD. First, some longitudinal studies indicate that RC often is a transient, rather than enduring, phenomenon in BD,13 in contrast to the nonvarying, trait feature of affective instability in persons with BPD. It is unknown whether URC is more enduring than transient. Notably, whereas bipolar mood episodes constitute deviations from a baseline state, affective instability in BPD is a baseline characteristic, rather than a deviation from it. Second, by definition, a BPD diagnosis hinges on additional elements unrelated to mood disturbances, such as interpersonal styles or defense mechanisms that involve splitting, projection, and projective identification, feelings of numbness, boredom, or emptiness, identity diffusion, fears of abandonment, and proclivities toward self-mutilation or other self-injurious behaviors as a means to alleviate tension and stress. These characteristics do not overlap with the core elements of BD.