123Bipolar and
 Related Disorders
Bipolar and related  disorders are separated from  the depressive disorders in
DSM-5 and placed between the chapters on schizophrenia spectrum and other psychotic
disorders and depressive disord ers in recognition of their place as a bridge between the
two diagnostic classes in terms of symptomato logy, family history, and genetics. The di-
agnoses included in this chapter are bipola r I disorder, bipolar II disorder, cyclothymic
disorder, substance/medication-induced bipo lar and related disorder, bipolar and relat-
ed disorder due to another medical condition, other specified bipolar and related disor-
der, and unspecified bipolar and related disorder.
The bipolar I disorder criter ia represent the modern understanding of the classic
manic-depressive disorder or affective psycho sis described in the ni neteenth century, dif-
fering from that classic description only to th e extent that neither psychosis nor the lifetime
experience of a major depressive episode is a requirement. However, the vast majority of
individuals whose symptoms meet the criter ia for a fully syndromal manic episode also
experience major depressive episodes during the course of their lives.
Bipolar II disorder, requiring the lifetime experience of at least one episode of major de-
pression and at least one hypomanic episode, is no longer thought to be a “milder” condition
than bipolar I disorder, largely because of th e amount of time individuals with this con-
dition spend in depression and because the in stability of mood experienced by individuals
with bipolar II disorder is typically accompanied by serious impairment in work and social
functioning.
The diagnosis of cyclothymic disorder is give n to adults who experience at least 2 years
(for children, a full year) of both hypomanic and depressive periods without ever fulfilling