The essential feature of cyclothymic disorder is a chronic, ﬂuctuating mood disturbance involving numerous periods of hypomanic symptoms and periods of depressive symp- toms that are distinct from each other (Criterion A). The hypomanic symptoms are of insufficient number, severity, pervasiveness, or duration to meet full criteria for a hypo- manic episode, and the depressive symptoms are of insufficient number, severity, perva— siveness, or duration to meet full criteria for a major depressive episode. During the initial 2-year period (1 year for children or adolescents), the symptoms must be persistent (pres— ent more days than not), and any symptom—free intervals last no longer than 2 months (Criterion B). The diagnosis of cyclothymic disorder is made only if the criteria for a major depressive, manic, or hypomanic episode have never been met (Criterion C).
If an individual with cyclothymic disorder subsequently (i.e., after the initial 2 years in adults or 1 year in children or adolescents) experiences a major depressive, manic, or hy- pomanic episode, the diagnosis changes to major depressive disorder, bipolar I disorder, or other specified or unspecified bipolar and related disorder (subclassified as hypomanic episode without prior major depressive episode), respectively, and the cyclothymic disor- der diagnosis is dropped.
The cyclothymic disorder diagnosis is not made if the pattern of mood swings is better explained by schizoaffective disorder, schizophrenia, schizophreniform disorder, delu- sional disorder, or other specified and unspecified schizophrenia spectrum and other psychotic disorders (Criterion D), in which case the mood symptoms are considered asso- ciated features of the psychotic disorder. The mood disturbance must also not be attribut- able to the physiological effects of a substance (e.g., a drug of abuse, a medication) or another medical condition (e.g., hyperthyroidism) (Criterion E). Although some individ- uals may function particularly well during some of the periods of hypomania, over the prolonged course of the disorder, there must be clinically significant distress or impair- ment in social, occupational, or other important areas of functioning as a result of the mood disturbance (Criterion F). The impairment may develop as a result of prolonged pe- riods of cyclical, often unpredictable mood changes (e.g., the individual may be regarded as temperamental, moody, unpredictable, inconsistent, or unreliable).
The lifetime prevalence of cyclothymic disorder is approximately 0.4%—1%. Prevalence in mood disorders clinics may range from 3% to 5%. In the general population, cyclothymic disorder is apparently equally common in males and females. In clinical settings, females with cyclothymic disorder may be more likely to present for treatment than males.
Cyclothymic disorder usually begins in adolescence or early adult life and is sometimes considered to reﬂect a temperamental predisposition to other disorders in this chapter.
Cyclothymic disorder usually has an insidious onset and a persistent course. There is a 15%—50% risk that an individual with cyclothymic disorder will subsequently develop bi- polar I disorder or bipolar II disorder. Onset of persistent, ﬂuctuating hypomanic and de- pressive symptoms late in adult life needs to be clearly differentiated from bipolar and related disorder due to another medical condition and depressive disorder due to another medical condition (e. g., multiple sclerosis) before the cyclothymic disorder diagnosis IS as- signed Among children with cyclothymic disorder, the mean age at onset of symptoms 15 6. 5 years of age.