Bipolar II involves one or more Major Depressive Episode and at least one Hypomanic Episode. A Hypomanic Episode is characterized by the same features as a Manic Episode, except that the symptoms may be present for as few as four days.  Additionally, in contrast with a Manic Episode, a Hypomanic Episode is not severe enough to cause marked impairment in social or occupational functioning or to require hospitalization, and there are never any psychotic features.

Bipolar I is characterized by the occurrence of one of more Manic Episode or Mixed Episodes.  A Manic Episode is defined by a period of abnormally and persistently elevated, expansive or irritable mood, lasting at least one week (or less if hospitalization is required).  The mood disturbance must be accompanied by at least three additional symptoms, including:

• Inflated self-esteem or grandiosity
• Decreased need for sleep
• Pressure speed
• Flight of ideas
• Distractibility
• Increased involvement in goal-directed activities
• Psychomotor agitation
• Excessive involvement in pleasure activities with a high potential for painful consequences

A mix episode is characterized by a one week period in which the criteria are met for both a Manic Episode and Major Depressive Episode nearly every day, and the person experiences rapidly alternating moods.