August 2006, Vol. XXIII, No. 9
Rapid cycling is included in DSM-IV as a course specifier for bipolar disorder (BP) I and II. However, its conceptualization remains controversial, and research concerning its treatment is still at an early stage. This article provides a synthesis of currently available evidence.
DEFINITION OF RAPID CYCLING
DSM-IV defines rapid cycling as the occurrence of at least 4 major depressive, manic, hypomanic, or mixed episodes during the previous year in a patient with a diagnosis of BP I or BP II. These episodes must be demarcated either by a partial or full remission of at least 2 months’ duration or by a switch to an episode of opposite polarity. Duration criteria for episodes are not waived, which means that each major depressive episode must last at least 2 weeks, each manic or mixed episode must last at least 1 week, and each hypomanic episode must last at least 4 days.
This definition has been criticized even by the leaders of the DSM-IV task force, who stated, In practice, some patients are encountered who have a large number of episodes, each of which has a brief duration of only a few days. Although such patients would not be diagnosed as having BP with rapid cycling in the conservative world of DSM-IV, they may present with similar course, management, and treatment response problems. The clinician may want to override this strict interpretation and consider such patients as rapid cycling.1
Actually, on the basis of the DSM-IV definition, a patient with BP who has had several direct transitions from one polarity of mood to the other during the previous year, but in whom most periods of abnormal mood have not fulfilled the duration criteria for an affective episode (Figure, patient A), may not be classified as a rapid cycler, whereas a patient with BP who has had a prolonged depressive recurrence with 3 partial remissions (Figure, patient B) during the previous year may be classified as a rapid cycler (since a bipolar course during the previous year is not required).
The fact is, however, that most clinicians and researchers would regard the first patient, and not the second, as a rapid cycler. Indeed, in several empiric studies on rapid cycling, duration criteria for affective episodes have been waived2-4; in some studies a circular course, ie, the direct transition from mania to depression or vice versa, has been required4; and in others, a continuous circular course, ie, the direct transition from mania to depression to mania, or from depression to mania to depression, has been a prerequisite.3
These differences in the definition of rapid cycling have important clinical implications. In a study published several years ago, my colleagues and I tested the reliability and validity of 4 alternative definitions of rapid cycling5:
The first requires at least 4 major depressive, manic, or hypomanic episodes, as defined by Research Diagnostic Criteria (RDC), during the previous year, demarcated by a euthymic period of at least 8 weeks or by a switch to an episode of opposite polarity.
The second is similar to the first but includes all major depressive, manic, or hypomanic episodes meeting RDC severity criteria and lasting at least 1 day.
The third is similar to the second but with the added requirement of at least 1 direct transition from mania or hypomania to major depression or vice versa during the previous year.
The fourth is similar to the second but with the added requirement of a total duration of fully symptomatic affective illness during the previous year of at least 8 weeks.
The highest interrater reliability (Cohen κ = 0.93) was obtained for the first definition (consistent with DSM-IV criteria). The Cohen κ values for the other 3 definitions were, respectively, 0.73, 0.75, and 0.80. Patients consistently identified as rapid cyclers by both assessing psychiatrists numbered 31 (14.8% of the entire sample of 210 bipolar patients recruited for the study) using the first definition, 57 (27.1%) using the second definition, 33 (15.7%) using the third definition, and 40 (19.0%) using the fourth definition.
Compared with non–rapid-cycling bipolar patients, there was a significantly higher proportion of women among the patients fulfilling the last 3 definitions for rapid cycling; and patients meeting the second and third definitions had a significantly higher frequency of the BP II pattern. Each group of rapid cyclers had a significantly lower proportion of patients with a favorable outcome with lithium(Drug information on lithium) prophylaxis compared with non–rapid cyclers, but the least significant difference was observed for patients fulfilling the first definition (P < .02 for this group, P < .0001 for the other 3 groups). During the followup period, a stability of the rapid cycling pattern was observed in 58.1% of patients fulfilling the first definition, and in 62.5%, 76.6%, and 45.2%, respectively, of those meeting the last 3 definitions. A summary of these results is given in Table 1.
Summary of the results of a study comparing 4 alternative definitions of rapid cycling5
|Definition||Interrater reliability||More women compared with NRC||More BP II compared with NRC||Worse lithium response than NRC||Stability of rapid cycling pattern (%)|
|Consistent with DSM-IV||0.93||No||No||Yes (P < .02)||58.1|
|Waiving duration criteria for affective episodes||0.73||Yes||Yes||Yes (P < .0001)||62.5|
|Waiving duration criteria and requiring
pole switching during
|0.75||Yes||Yes||Yes (P < .0001)||76.6|
|Waiving duration criteria and requiring
at least 8 weeks of fully
illness during previous year
|0.80||Yes||No||Yes (P < .0001)||45.2|
NRC, non–rapid cyclers; BP, bipolar disorder.