There are a number of bipolar and related disorders.
Bipolar I disorder
Bipolar I disorder is characterised by one or more manic episodes (which last at least one week). Episodes of either depression or hypomania may also occur prior to or following a manic episode. Due to the severe nature of these symptoms, people with bipolar I disorder may require hospitalisation during an episode.
Bipolar II disorder
Bipolar II disorder is characterised by both hypomanic and depressive episodes but unlike bipolar I disorder, no manic episodes are experienced. Hypomania represents a change to the person’s usual functioning (noticeable by others) but is not, by definition, associated with impairment. Although bipolar II disorder is less severe than bipolar I disorder in terms of symptoms, it can be more chronic as depressive symptoms are often more frequent and longer-lasting.
Cyclothymic disorder
Cyclothymic disorder is characterised by persistent and unpredictable changes in mood but without the extreme highs and lows of bipolar I and II disorder, with episodes of shorter duration.