Conditions for Further Study 789
2–3 days of hypomanic symptoms. Once an individual has experienced a hypomanic ep-
isode (4 days or more), the diagnosis beco mes and remains bipolar II disorder regardless
of future duration of hy pomanic symptom periods. 
Major depressive disorder. Major depressive disorder is al so characterized by at least
one lifetime major depressive ep isode. However, the additional presence of at least two life-
time periods of 2–3 days of hypomanic symptoms leads to a diagnosis of short-duration hy-
pomania rather than to major depressive disorder.  
Major depressive disorder with mixed features. Both major depressive disorder with
mixed features and short-duration hypomania are characterized by the presence of some
hypomanic symptoms and a major depressive episode. However, major depressive disor-
der with mixed features is characteri zed by hypomanic features present concurrently  with
a major depressive episode, while individual s with short-duration hypomania experience
subsyndromal hypomania and fully syndroma l major depression at different times.
Bipolar I disorder. Bipolar I disorder is differentiat ed from short-duration hypomania
by at least one lifetime manic episode, which is longer (at least 1 week) and more severe
(causes more impaired social functioning) than a hypomanic episode. An episode (of any
duration) that involves psychotic symptoms or necessitates hospitalization is by definition
a manic episode rather than a hypomanic one.
Cyclothymic disorder. While cyclothymic disorder is characterized by periods of de-
pressive symptoms and periods of hypomanic symptoms, the lifetime presence of a major
depressive episode precludes the di agnosis of cyclothymic disorder. 
Comorbidity