Ultra-rapid cycling (URC) entered the psychiatric lexicon in the 1990s as a proposed descriptor for manic/hypomanic, mixed, or depressed episodes of bipolar disorder (BD) that occur every few days or weeks. DSM-IV-TR incorporates rapid cycling (RC)—but not URC—as a course specifier that occurs in 10% to 15% of patients with BD who have ≥4 distinct affective episodes per year, each fulfilling duration criteria and separated by identifiable recovery periods (unless an episode directly changes polarity). Since then, the terms RC and URC have seemingly metamorphosed into imprecise, popular colloquialisms meant to loosely describe frequent mood changes rather than distinct episodes over extended time periods, with little regard for the associated signs that define manic or hypomanic episodes.
This article examines the meaning and validity of URC in BD, its relevance and differentiation from rapid mood shifts in patients without BD, and concepts relevant to treatment extrapolated from studies of RC BD.
Post et al1 coined the terms “ultra-rapid cycling” and “ultra-ultra-rapid cycling” (also called “ultradian cycling”) to describe mood episodes that occur monthly (URC) or over the course of as little as 1 day (ultradian cycling). These constructs are controversial because they lack demonstrated content validity and discriminant validity relative to other disorders. (“Content validity” refers to whether the features thought to comprise an entity of interest accurately and meaningfully do so; “discriminant validity” tells researchers and clinicians whether the proposed description of a clinical entity uniquely differentiates it from other disorders—avoiding “false-positive” suspected cases.) Clinicians therefore must pay careful attention to non-bipolar psychiatric problems that can present with rapid mood changes but without the psychomotor and related signs that define bipolar mood episodes. In their looser, nontechnical meanings, “rapid cycling” or “ultra-rapid cycling” may be synonymous with affective lability. RC is neither a diagnosis in itself nor a criterion for diagnosing BD. Rather, it is a course specifier to describe episode frequency in patients with past unambiguous manic or hypomanic episodes.
In children and adolescents, whose presentations often are atypical and can be hard to differentiate from other forms of behavioral or temperamental dysregulation, severe non-episodic mood dysregulation without signs of mania or hypomania may indicate a phenomenon separate from BD.2 Geller and colleagues3 proposed using the term “episodes” to frame the duration of a DSM-IV-defined syndrome of mania/hypomania or depression, while reserving the term “cycling” to connote patterns of mood alternation within a given episode. It is not clear whether this concept of “cycling” differs qualitatively from mood lability that arises during a mood episode in children or adults, and notably, this perspective does not account for changes in psychomotor signs in conjunction with changes in mood.
Clinicians also sometimes blur the concept of “mixed episodes” with RC or URC. DSM-IV-TR defines mixed episodes within bipolar I disorder (BD I) based on criteria for a simultaneous manic and depressive episode, rather than on frequent oscillations between affective poles. These and other differential diagnostic considerations for suspected URC are summarized in Table 1.4
A further concern regarding nomenclature involves the distinction between cyclicity (ie, successive episodes regardless of pole direction) and changes in polarity (ie, switches from depression to mania/hypomania or vice versa). Some mood disorder patients may have rapid oscillations from euthymia to depression while never changing polarity to mania/hypomania and may be best described as having recurrent brief depression.
Differential diagnosis in suspected URC
|Phenomenon||Considerations for assessment|
|Mixed episodes in bipolar I disorder, or mixed depressive episodes in bipolar II disorder||DSM-IV-TR mixed episodes entail the co-occurrence of manic and depressive symptoms during the same episode without an intervening period of recovery. ICD-10 includes “rapid alternation of manic, hypomanic or depressive symptoms…from day to day or even hour to hour” in its definition of a mixed episode|
|Distress responses to acute environmental adversities (eg, adjustment disorders with mixed disturbance of emotions and conduct)||One would expect an absence of corresponding sleep-wake cycle changes or speech-language and psychomotor disturbances|
|Intoxication/withdrawal from psychoactive substances or drug-induced mental status changes (eg, corticosteroids, amphetamine, cocaine); a history of substance abuse also may be associated with development of URC in BD patients4||Substance-induced mood fluctuations caused by intoxication/withdrawal can mimic affective cycling|
|Disinhibition states and frontal lobe syndromes as seen in traumatic brain injury and other CNS disorders, such as multiple sclerosis||Assess for signs of perseveration and history of head trauma or neurologic damage from cumulative toxic-metabolic insults (eg, chronic alcoholism)|
|Autonomic hyperarousal, emotional volatility, and hyperreactivity to environmental stresses, suggestive of PTSD||Determine the presence of a trauma history and review whether DSM-IV-TR symptoms and associated features of PTSD exist, including re-experiencing/reliving and avoidance, as well as paranoid thinking, dissociation, and nightmares|
|Recurrent mood shifts related to premenstrual dysphoric disorder may mimic URC. Other endocrine dysfunctions also may present with URC (eg, thyroid or ovarian malignancies)||Affirm the independent presence of BD before inferring its manifestations solely from premenstrual mood changes|
|Trait affective instability associated with borderline personality disorder||Trait mood instability is more chronic and enduring than episodic, and would not be expected to occur in tandem with signs of psychomotor activation that define mania/hypomania|
|BD: bipolar disorder; ICD-10: International Statistical Classification of Diseases and Related Health Problems, 10th revision; PTSD: posttraumatic stress disorder; URC: ultra-rapid cycling|