explained by schizoaffective disorder, schizophrenia, schizophreniform disorder, delu-
sional disorder, or other specified and un specified schizophrenia spectrum and other
psychotic disorders (Criterion D), in which c ase the mood symptoms are considered asso-
ciated features of the psychoti c disorder. The mood disturbanc e must also not be attribut-
able to the physiological effe cts of a substance (e.g., a dr ug of abuse, a medication) or
another medical condition (e.g., hyperthyroidis m) (Criterion E). Although some individ-
uals may function particularly  well during some of the pe riods of hypomania, over the
prolonged course of the disorder , there must be clinically significant distress or impair-
ment in social, occupational, or other import ant 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 ch anges (e.g., the individual may be regarded
as temperamental, moody, unpredicta ble, inconsistent , or unreliable).
Prevalence
The lifetime prevalence of cyclothymic diso rder is approximately 0.4%–1%. Prevalence in
mood disorders clinics may rang e 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 lik ely to present for tr eatment than males.
Development and Course
Cyclothymic disorder usually begins in adolescence or early adult life and is sometimes
considered to reflect a temperamental predispo sition to other disorders in this chapter.
Cyclothymic disorder usually has an insidious onset and a persistent course. There is a