Version July 2025
INTRODUCTION —
Bipolar disorder is characterized by mood episodes that are nearly always recurrent [1,2]. Among patients who experience at least four episodes during a 12-month period, the mood disorder specifier “with rapid cycling” is required as part of the diagnosis to describe the course of illness, according to the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR) [1].
The term “rapid cycling” was first used in 1974 to describe bipolar patients who were relatively unresponsive to lithium [3]. However, it is now clear that pharmacotherapy in general is typically less effective for rapid cycling patients than for nonrapid cycling patients [4,5].
This topic reviews the epidemiology, pathogenesis, clinical features, and diagnosis of rapid cycling in patients with bipolar disorder. Treatment of rapid cycling is discussed separately, as is the diagnosis and treatment of the general population of patients with bipolar disorder:
●(See "Rapid cycling bipolar disorder in adults: Treatment of major depression".)
●(See "Rapid cycling bipolar disorder in adults: Treatment of mania and hypomania".)
●(See "Bipolar disorder in adults: Assessment and diagnosis".)
●(See "Bipolar mania and hypomania in adults: Choosing pharmacotherapy".)
●(See "Bipolar major depression in adults: Choosing treatment".)
●(See "Bipolar disorder in adults: Choosing maintenance treatment".)
DEFINITIONS —
Bipolar disorder is characterized by episodes of mania (table 1), hypomania (table 2), and major depression (table 3) [1]. Subtypes of bipolar disorder include bipolar I and bipolar II:
●Bipolar I disorder – Patients with bipolar I disorder experience manic episodes, and nearly always experience major depressive and hypomanic episodes.
●Bipolar II disorder – Bipolar II disorder is marked by a history of at least one hypomanic episode, at least one major depressive episode, and the lifetime absence of manic episodes.
Most patients with bipolar disorder suffer from multiple mood episodes over their lifetime. In patients who experience at least four episodes during a 12-month period, the diagnostic criteria require the mood disorder specifier “with rapid cycling” as part of the diagnosis to describe the course of illness (eg, “bipolar I disorder with rapid cycling”).
Additional information about the clinical features and diagnosis of bipolar disorder, including mood episodes and mood disorder specifiers, is discussed separately. (See "Bipolar disorder in adults: Clinical features" and "Bipolar disorder in adults: Assessment and diagnosis", section on 'Diagnosis'.)
EPIDEMIOLOGY
Prevalence — The prevalence of a rapid cycling course of illness in bipolar disorder has been examined in community surveys of the general population and in studies of patients with bipolar disorder.
●General population – A cross-national community study (n>54,000 individuals in 10 countries) found that the estimated one-year prevalence of rapid cycling bipolar disorder in the general population was 0.3 percent [6]. The prevalence ranged from 0.0 percent in Bulgaria, India, and Japan to 0.7 percent in the United States.
●Patients with bipolar disorder – Among patients with bipolar disorder, the estimated one-year prevalence of rapid cycling ranges from 22 to 30 percent, depending upon the setting, and the lifetime prevalence is 36 percent [5,6].
Sociodemographic correlates
●Age of onset – Onset of bipolar disorder may occur earlier in patients who develop rapid cycling bipolar disorder, compared with nonrapid cycling bipolar disorder, but the difference is small [7]. In a cross-national community study, onset of bipolar disorder occurred at a younger age among rapid cycling individuals compared with nonrapid cycling individuals (mean age 17 versus 20 years) [6].
●Sex – Based upon a systematic review of 30 studies in patients with bipolar disorder (n>13,000), the association between female sex and rapid cycling is modest at most [5-8].
PATHOGENESIS —
Although the pathogenesis of rapid cycling in bipolar disorder is not known, its development may involve antidepressants and childhood maltreatment.
Role of antidepressants — Although it is plausible that antidepressants (eg, tricyclics) can trigger and prolong rapid cycling bipolar disorder [9,10], this is not established and remains a point of contention [11-16], due to the low-quality, inconclusive evidence that is available [5,17]:
●A few prospective observational studies have found an association between antidepressants and rapid cycling. As an example, the Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD) study followed 1191 bipolar patients for up to one year and found that rapid cycling occurred nearly four times more often in patients who received antidepressants compared with patients who did not [18].
In addition, a prospective study compared 159 rapid cycling patients with 567 nonrapid cycling patients and found that treatment with antidepressants was associated with greater irritability and treatment resistance in rapid cycling patients [19].
●By contrast, other studies refute the association between antidepressants and the emergence of rapid cycling. In one study that followed 345 bipolar patients for a mean of 14 years, antidepressants were not associated with onset of rapid cycling and resolution of rapid cycling was not associated with discontinuation of antidepressants [20].
Additional indirect evidence from both short-term (eg, ≤6 months) and long-term (>6 months) randomized trials indicate that adjunctive antidepressants may not cause or exacerbate rapid cycling and are safe to use in many patients with rapid cycling [14]. In so far as patients are not switching from major depression to mania/hypomania, they may not be at increased risk of rapid cycling. (See "Bipolar major depression in adults: Efficacy and adverse effects of antidepressants", section on 'Risk of switching to mania'.)
An alternative hypothesis for the association between antidepressants and rapid cycling is that frequent episodes of major depression are a feature of rapid cycling disorder rather than the antidepressants being a cause of rapid cycling [21].
The role of antidepressants in treating rapid cycling patients with major depression is discussed separately. (See "Rapid cycling bipolar disorder in adults: Treatment of major depression", section on 'Resistant patients'.)
Other implicated factors
●Childhood maltreatment – A history of childhood maltreatment is associated with rapid cycling [5]. In a meta-analysis of eight studies (n>3000 patients with bipolar disorder), the odds of rapid cycling was nearly two times greater in bipolar patients with a history of childhood maltreatment (physical, sexual, or emotional abuse; neglect; or family conflict), compared to patients without a history of maltreatment (odds ratio 1.9, 95% CI 1.5-2.5) [22]. A subsequent study also found that more patients with rapid cycling reported childhood sexual abuse than nonrapid cycling patients (29 versus 16 percent) [23].
●Genetics – There is considerable evidence for the genetic transmission of bipolar disorder. (See "Bipolar disorder in adults: Epidemiology and pathogenesis", section on 'Genetics'.)
However, support for the heritability of a rapid cycling course is minimal [5], and multiple studies have failed to demonstrate that genetic factors are involved in rapid cycling. As an example, a meta-analysis of four family history studies (693 bipolar patients, including 146 with rapid cycling) found that rapid cycling did not aggregate within families [11]; a subsequent study also failed to find evidence that rapid cycling is a familial trait [24]. In addition, linkage studies have not consistently identified any specific genes associated with rapid cycling [5,25-30].
●Hypothyroidism – Across multiple studies, the evidence for an association between hypothyroidism and rapid cycling bipolar disorder is inconsistent [5]. Whereas some studies have found an association between the two, other studies have found that hypothyroidism was present in a comparable number of rapid cycling and nonrapid cycling patients [11,23].
●Neurobiologic correlates – Although biomarkers specific for rapid cycling bipolar disorder have not been established, different biologic correlates of rapid cycling bipolar disorder have been identified [31]. However, it is not clear whether these findings represent etiologic causes or sequelae of the disorder because the studies investigated patients who already met criteria for rapid cycling.
Neuroimaging studies have detected several correlates of rapid cycling. As an example, magnetic resonance imaging (MRI) studies have found that the ventral prefrontal cortex is smaller in rapid cycling patients than in nonrapid cycling patients [32,33], and that other gray matter structures are smaller in rapid cycling patients compared with healthy controls [32].
CLINICAL FEATURES
Underlying bipolar disorder
●Onset of rapid cycling – Rapid cycling bipolar disorder can occur at any point during the course of illness in bipolar disorder. As an example, a review of studies that included 181 rapid cycling patients found that rapid cycling was present at the onset of bipolar disorder in 27 percent [11]. By contrast, a study of 109 bipolar patients with past-year rapid cycling found that onset of rapid cycling followed onset of bipolar disorder by a mean of 11 years [34]. In addition, case reports describe onset of rapid cycling in geriatric bipolar patients [35,36].
●Bipolar I and bipolar II disorder subtypes – It is not clear whether the prevalence of rapid cycling differs between bipolar I and bipolar II disorder. Some studies suggest that the frequency of rapid cycling does not differ substantially across the two subtypes of bipolar disorder [5,6,19,37], other studies found a history of rapid cycling in more bipolar II patients than bipolar I patients [8,11,23], and yet another study found that the prevalence of rapid cycling was greater in bipolar I patients [38].
Characteristics of mood episodes
●Defining features of episodes – Rapid cycling bipolar disorder is by characterized mood episodes of mania (table 1), hypomania (table 2), and/or major depression (table 3) [1,5]. The episode symptoms that occur as part of a rapid cycling pattern are no different from those that occur as part of a nonrapid cycling pattern.
Separate mood episodes are demarcated from each other by either of the following [1]:
•Switching from one pole to the other – Manic and hypomanic episodes are counted as being on the same pole; thus, a switch in polarity involves either an episode of mania or hypomania and an episode of major depression [1]. As an example, in a patient with mania, the symptoms may cease, replaced by symptoms of major depression. The time frame for switching poles is less than two months between the point that the patient has remitted from a mood episode on one pole and the point that the patient becomes ill with an episode on the other pole.
•Full or partial remission for at least two months – As an example, an episode of bipolar major depression may remit, and be followed by a period of euthymia for three months and then another episode of depression.
Although there is no established definition for partial remission, most authorities define it as stabilization of the patient’s safety and substantial improvement in the number, intensity, and frequency of mood and psychotic symptoms. Partial remission can be quantified with standardized rating scales that assess mania (eg, the Young Mania Rating Scale [39]), depression (eg, the Patient Health Questionnaire – Nine Item (table 4) [40]), and psychosis (eg, the Brief Psychiatric Rating Scale [41]), but this is not standard clinical practice.
●Type of mood episodes – The mood episodes that arise during rapid cycling can occur in any combination.
The predominant psychopathology in rapid cycling bipolar disorder is generally depression, rather than mania or hypomania [23,42]. As an example, among 206 bipolar patients who suffered rapid cycling during prospective follow-up lasting one year, depressive symptoms were present for twice as many days as were manic/hypomanic symptoms (145 versus 73 days) [38]. This is consistent with the finding that depression is the predominant mood state for the general population of bipolar patients. (See "Bipolar disorder in adults: Clinical features", section on 'Major depression'.)
Rapid cycling bipolar disorder often includes brief mood states or “truncated episodes” with manic, hypomanic, and/or depressive symptoms that meet DSM-5-TR symptom criteria but not duration criteria for a mood episode. A one-year prospective study of 206 rapid cycling patients found that in addition to full mood episodes, the average number of truncated episodes was nine [38]. However, it is difficult to distinguish multiple truncated mood episodes from a single episode with mixed features (concurrent symptoms of major depression and mania/hypomania) [1].
It is not clear whether the frequency of psychotic features differs between patients with rapid cycling and nonrapid cycling bipolar disorder. Whereas some studies have found that psychotic features occurred more often in rapid cycling bipolar disorder than nonrapid cycling bipolar disorder [7,43], other studies suggest that a lifetime history of psychotic mood episodes is comparable in rapid cycling and nonrapid cycling patients [37,38].
●Sequence of mood episodes – The sequence of mood episodes observed during rapid cycling varies greatly; a few examples include (figure 1) [44]:
•Individual mood episodes that are each followed by a period of euthymia.
•Continuous cycling – Alternating episodes of opposite polarity (major depression on one pole and manic/hypomanic episodes on the other pole) that are immediately contiguous with each other or separated by less than eight weeks of remission.
•Numerous mood episodes that form no discernible pattern.
Functional impairment — Psychosocial functioning is generally more impaired in rapid cycling than nonrapid cycling bipolar disorder [7,20,37,38,45]. A cross-national community study found that during bipolar depressive episodes in the past year, severe role impairment occurred in more rapid cycling patients than nonrapid cycling patients (87 versus 67 percent) [6]. During manic/hypomanic episodes, rapid cycling patients were unable to function for more days than nonrapid cycling patients (51 versus 21 days).
Functional impairment in patients with rapid cycling may be due to an increased number of mood episodes. In addition, a shorter time in remission between mood episodes can hinder functional recovery.
Suicide attempts — Among patients with bipolar disorder, rapid cycling is associated with an increased risk of suicide attempts [5,23]. In a meta-analysis of 9 studies involving patients with rapid cycling (n = 1668) or nonrapid cycling bipolar disorder (n = 4900), the lifetime prevalence of suicide attempts was greater in those with rapid cycling (47 versus 30 percent) [46]. In a subsequent study, the mean lifetime number of suicide attempts was greater in rapid cycling than nonrapid cycling patients (1.0 versus 0.6) [19].
COMORBIDITY —
Comorbid psychiatric and general medical disorders are common in patients with rapid cycling bipolar disorder.
●Psychiatric disorders – Rapid cycling bipolar patients are more likely than nonrapid cycling patients to have a lifetime history of comorbid psychopathology, including [6,19,38]:
•Anxiety disorders (eg, panic disorder, generalized anxiety disorder, and social phobia)
•Attention deficit hyperactivity disorder
•Bulimia nervosa
•Obsessive-compulsive disorder
•Substance-related and addictive disorders
In addition, impulsivity is greater in rapid cycling bipolar disorder than nonrapid cycling bipolar disorder [47].
●General medical disorders – Multiple general medical illnesses are frequently observed in patients with rapid cycling [7]; one study (n = 225) found that the mean number of medical comorbidities was 2.5 [48]. Also, a prospective study of bipolar patients with type 2 diabetes (n = 26) and euglycemic bipolar patients (n = 56) found that rapid cycling occurred in more patients with type 2 diabetes than euglycemic patients (39 versus 18 percent) [49]. Other organ systems that are commonly affected in rapid cycling bipolar disorder include respiratory, musculoskeletal, neurologic, endocrine/metabolic, and genitourinary [7,19,50,51].
In addition, some medical illnesses may occur more frequently in rapid cycling bipolar disorder than nonrapid cycling bipolar disorder [23].
COURSE OF ILLNESS
Duration — Rapid cycling bipolar disorder is generally a temporary phenomenon (state) rather than a longer-term stable characteristic (trait) [18,45]. In prospective studies of patients with rapid cycling (n = 89 and 356), onset of rapid cycling was followed by conversion to nonrapid cycling within one to three years in approximately 90 percent [18,20]. Another prospective study (n = 118 rapid cycling patients) found that rapid cycling resolved in 80 percent [23].
Nevertheless, rapid cycling can persist longer (eg, eight years) [34]. One factor associated with persistent rapid cycling is a depression-(hypo)mania-interval course; the interval is characterized by full or partial remission. Other factors associated with a relatively long duration include a sudden “switch” from depression to (hypo)mania, and the occurrence of agitated/mixed depressive episodes.
Once rapid cycling resolves, the risk for a subsequent period of rapid cycling is not known.
Prognosis — Bipolar patients who suffer rapid cycling at some point in their course of illness generally have a poorer long-term prognosis (with more lifetime affective morbidity), compared with nonrapid cycling patients [12,20,38]. As an example, a cross-national community study found that the number of lifetime mood episodes was greater in rapid cycling than nonrapid cycling patients (103 versus 28 episodes), as was the number of lifetime years with at least one episode (15 versus 6 years) [6].
Nevertheless, bipolar patients who at one point experience rapid cycling may recover from bipolar disorder. In a study of 109 bipolar patients with rapid cycling who were followed prospectively for up to 36 years, 33 percent recovered from bipolar disorder (defined as no recurrent mood episodes for at least one year); the mean duration of recovery was 11 years [34].
ASSESSMENT AND DIAGNOSIS
Assessment — The initial clinical evaluation of patients with a possible diagnosis of rapid cycling bipolar disorder includes a psychiatric and general medical history, mental status and physical examination, and focused laboratory tests [52-54]. The psychiatric history should emphasize the number of major depressive (table 3), manic (table 1), and hypomanic (table 2) episodes during the previous 12 months (current rapid cycling), as well as any prior 12-month periods (lifetime rapid cycling) [1]. Patients may have difficulty distinguishing past mood episodes when they are not separated by relatively long intervals of euthymia; interviewing family members may help to determine the number and type of mood episodes that have occurred. The demarcation between separate mood episodes is discussed elsewhere in this topic. (See 'Diagnostic criteria' below.)
No self-report instrument is available to screen specifically for rapid cycling bipolar disorder. Information about assessing bipolar patients in general is discussed separately. (See "Bipolar disorder in adults: Assessment and diagnosis", section on 'Assessment'.)
Diagnostic criteria — According to DSM-5-TR, the essential feature of rapid cycling is the occurrence of four or more bipolar mood episodes within a 12-month period [1]. Thus, the term rapid cycling is used to specify the course of illness, rather than a subtype of bipolar disorder.
The following subtypes of bipolar disorder may warrant a rapid cycling specifier:
●Bipolar I disorder – Patients with bipolar I disorder experience manic episodes (table 1), and nearly always experience hypomanic (table 2) and major depressive episodes (table 3). As an example, for patients with bipolar I disorder who experience at least four mood episodes during a 12-month period, the diagnosis is “bipolar I disorder with rapid cycling.”
●Bipolar II disorder – Bipolar II disorder is marked by a history of at least one hypomanic episode, at least one major depressive episode, and the lifetime absence of manic episodes.
Any bipolar I or bipolar II patient can develop rapid cycling and then subsequently revert to a nonrapid cycling course [16].
Beyond bipolar I and bipolar II disorder, the rapid cycling specifier is not used to characterize the course of illness in other DSM-5-TR bipolar and related disorders [1].
Additional information about diagnosing each bipolar subtype is discussed separately. (See "Bipolar disorder in adults: Assessment and diagnosis", section on 'Bipolar disorders'.)
●Rapid cycling – According to DSM-5-TR, the diagnostic criteria for rapid cycling are as follows [1]:
•At least four bipolar mood episodes in a 12-month period.
•The episodes meet both the symptom and duration criteria for major depression (table 3), mania (table 1), or hypomania (table 2); the episodes that occur as part of a rapid cycling pattern are no different from episodes that occur as part of a nonrapid cycling pattern. Mood episodes that are directly caused by substance intoxication (eg, cocaine or corticosteroids) or a general medical disorder do not count toward defining a rapid cycling pattern.
•The mood episodes can occur in any order or combination.
•Separate mood episodes are demarcated from each other by either of the following:
-Switching from one pole to the other – Manic and hypomanic episodes are counted as being on the same pole; thus, a switch in polarity involves either an episode of mania or hypomania and an episode of major depression [1]. As an example, in a patient with mania, the symptoms may cease, replaced by symptoms of major depression. The time frame for switching poles is less than two months between the point that the patient has remitted from a mood episode on one pole and the point that the patient becomes ill with an episode on the other pole. In some cases, patients may switch immediately from one pole to the other.
-Full or partial remission for at least two months – As an example, an episode of bipolar major depression may remit, and be followed by a period of euthymia for three months and then another episode of depression.
Although there is no established definition for partial remission, most authorities define it as stabilization of the patient’s safety and substantial improvement in the number, intensity, and frequency of mood and psychotic symptoms. Partial remission can be quantified with standardized rating scales that assess mania (eg, the Young Mania Rating Scale [39]), depression (eg, the Patient Health Questionnaire – Nine Item (table 4) [40]), and psychosis (eg, the Brief Psychiatric Rating Scale [41]), but this is not standard clinical practice.
Patients who manifest brief mood states in the absence of full-duration mood episodes are classified as other specified bipolar disorder, without the additional course specifier rapid cycling. Rapid shifts between mood states have been described in case reports as “ultra-rapid cycling,” in which patients alternate between periods of mania/hypomania, depression, and euthymia, with each mood state lasting approximately 24 hours [55,56]. “Ultradian cycling” has also been described, consisting of shifts between different mood states (lasting only several hours), occurring within one day [56,57]. The mood states seen during ultra-rapid cycling and ultradian cycling do not meet duration criteria for mood episodes as defined in the DSM-5-TR [1].
The World Health Organization's International Classification of Diseases-11th Revision (ICD-11), which has been harmonized with the DSM-5-TR, also includes a rapid cycling specifier for bipolar type I and II disorder [58].
Many authorities think it is arbitrary to use a cut-off of four mood episodes to define rapid cycling bipolar disorder [15,16,18,21,38,45]. Although this cut-off was confirmed to some degree in studies that examined the validity of rapid cycling, subsequent studies that examined the stability, course of illness, and heritability of rapid cycling did not support this cut-off. In addition, the number of mood episodes observed in bipolar patients during a specific time period is distributed monotonically along a continuum [21,24,38,45]. Thus, rapid cycling appears to represent one extreme on the spectrum of episode frequency that occurs in bipolar disorder [24,38].
Differential diagnosis — The psychopathology of rapid cycling bipolar disorder overlaps with that of borderline personality disorder [16,45]. In addition, the two disorders often co-occur in the same patient [59].
The clinical features of rapid cycling bipolar disorder overlap with those of borderline personality disorder in that the rapid switches between mood elevation (mania or hypomania) and major depression that can occur in rapid cycling may resemble the mood lability that occurs in borderline personality disorder [1,45]. However, the affective instability of borderline patients is generally a reaction to environmental triggers such as perceived rejection or failure, which is typically not the case in rapid cycling patients. In addition, borderline personality disorder is marked by unstable and intense interpersonal relationships, identity disturbance (unstable self-image or sense of self), chronic feelings of emptiness, and frantic efforts to avoid abandonment; these features are not characteristic of rapid cycling bipolar disorder [1].
Additional information about the differential diagnosis of bipolar disorder in general is discussed separately. (See "Bipolar disorder in adults: Assessment and diagnosis", section on 'Differential diagnosis'.)
INFORMATION FOR PATIENTS —
UpToDate offers two types of patient education materials, “The Basics” and “Beyond the Basics.” The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on “patient info” and the keyword(s) of interest.)
●Basics topics (See "Patient education: Bipolar disorder (The Basics)" and "Patient education: Coping with high drug prices (The Basics)".)
●Beyond the Basics topics (See "Patient education: Bipolar disorder (Beyond the Basics)" and "Patient education: Coping with high prescription drug prices in the United States (Beyond the Basics)".)
These educational materials can be used as part of psychoeducational psychotherapy. (See "Bipolar disorder in adults: Psychoeducation and other adjunctive maintenance psychotherapies", section on 'Group psychoeducation'.)
The National Institute of Mental Health also has educational material explaining the symptoms, course of illness, and treatment of bipolar disorder in a booklet entitled "Bipolar Disorder," which is available online at the website or through a toll-free number, 866-615-6464. The website also provides references, summaries of study results in language intended for the lay public, and information about clinical trials currently recruiting patients.
More comprehensive information is provided in many books written for patients and family members, including The Bipolar Disorder Survival Guide: What You and Your Family Need to Know, Third Edition, written by David J. Miklowitz, PhD (published by The Guilford Press, 2019); An Unquiet Mind: A Memoir of Moods and Madness, written by Kay Jamison, PhD (published by Random House, 1995); and Treatment of Bipolar Illness: A Casebook for Clinicians and Patients, by RM Post, MD, and GS Leverich, LCSW (published by Norton Press, 2008).
The Depression and Bipolar Support Alliance (accessible at the website or 800-826-3632) is a national organization that educates members about bipolar disorder and how to cope with it. Other functions include increasing public awareness of the illness and advocating for more research and services. The organization is administered and maintained by patients and family members, and has local chapters.
The National Alliance on Mental Illness (accessible at the website or 800-950-6264) is a similarly structured organization devoted to education, support, and advocacy for patients with any mental illness. Bipolar disorder is one of their priorities.
SUMMARY AND RECOMMENDATIONS
●Definition of bipolar disorder – Bipolar disorder is characterized by episodes of mania (table 1), hypomania (table 2), and major depression (table 3). (See 'Definitions' above and "Bipolar disorder in adults: Clinical features", section on 'Clinical presentation' and "Bipolar disorder in adults: Assessment and diagnosis", section on 'Diagnosis'.)
●Rapid cycling
•Prevalence – Among patients with bipolar disorder, the estimated one-year prevalence of rapid cycling ranges from 22 to 30 percent, depending upon the setting, and the lifetime prevalence is 36 percent. (See 'Prevalence' above.)
•Pathogenesis – The pathogenesis of rapid cycling bipolar disorder is not known. Although some clinical observations suggest that antidepressants may trigger and prolong rapid cycling bipolar disorder, this is not established. (See 'Pathogenesis' above.)
•Clinical features
-Underlying bipolar disorder – Onset of rapid cycling can occur at any point during the course of illness in bipolar disorder. (See 'Underlying bipolar disorder' above.)
-Characteristics of mood episodes – Rapid cycling bipolar disorder is by characterized mood episodes of mania (table 1), hypomania (table 2), and/or major depression (table 3). The episode symptoms that occur as part of a rapid cycling pattern are no different from those that occur as part of a nonrapid cycling pattern.
Although the mood episodes that arise during rapid cycling can occur in any combination, the predominant psychopathology in rapid cycling bipolar disorder is generally depression, rather than mania or hypomania.
The sequence of mood episodes observed during rapid cycling varies greatly (figure 1).
Psychosocial functioning is generally more impaired in rapid cycling than nonrapid cycling bipolar disorder.
(See 'Characteristics of mood episodes' above.)
-Suicide attempts – Nearly 50 percent of patients with a history of rapid cycling bipolar disorder attempt suicide during their lifetime. (See 'Suicide attempts' above.)
•Comorbidity – Comorbid psychopathology is more common in rapid cycling patients than nonrapid cycling patients. (See 'Comorbidity' above.)
•Course of illness – Rapid cycling bipolar disorder is generally a transient phenomenon; however, some patients may experience rapid cycling for longer periods.
Bipolar patients who suffer rapid cycling generally have a poorer long-term course of bipolar disorder, compared with nonrapid cycling patients. (See 'Course of illness' above.)
•Assessment – The initial clinical evaluation of patients with a possible diagnosis of rapid cycling bipolar disorder includes a psychiatric and general medical history, mental status and physical examination, and focused laboratory tests. The psychiatric history should emphasize the number of mood episodes during the previous 12 months, as well as any previous 12-month period. (See 'Assessment' above.)
•Diagnosis – Rapid cycling bipolar disorder is diagnosed in patients with four or more mood episodes during a 12-month period. Separate mood episodes are demarcated from each other either by a switch from one pole to the other (eg, major depression to hypomania/mania), or by full or partial remission for at least two months. However, many authorities think it is arbitrary to use a cut-off of four mood episodes to define rapid cycling bipolar disorder, and conceptualize rapid cycling as one extreme on the spectrum of episode frequency that occurs in bipolar disorder. (See 'Diagnostic criteria' above.)
•Differential diagnosis – The clinical features of rapid cycling bipolar disorder overlap with those of borderline personality disorder, but the two can generally be distinguished by a detailed history. (See 'Differential diagnosis' above.)
