Individuals with Bipolar I Disorder have experienced one or more Manic or Mixed Episodes and often have had one or more Depressive Episodes, though a Depressive Episode is not necessary to meet diagnosis criteria.  A Manic Episode is marked by a significant period of abnormally and persistently elevated, expansive, or irritable mood, lasting at least one week.  Additional characteristics include at least three of the following or four if the mood is irritable:

• Inflated self-esteem or grandiosity
• Decreased need for sleep
• More talkative and/or pressure to keep talking
• Flight of ideas or racing thoughts
• Distractibility
• Increase in goal directed activity
• Excessive involvement in pleasurable activities with a potential for negative consequences

There is also marked impairment in social and occupational functioning.

A Mixed Episode is defined by a period of time (at least 1 week) in which, the criteria for a Major Depressive Episode and a Manic Episode are both met.  This period is marked by a rapidly changing mood.

American Psychiatric Association: Diagnostic and Statistical Manual of Mental Disorders, Fourth  Edition, text Revision. Washington, DC American Psychiatric Association, 2000.