People with bipolar disorder experience extremes of mood, known as mania and depression.

During a manic period, an individual might feel euphoric, powerful, creative and unstoppable. The highs may start out as exciting, productive and social, but can progress into psychosis.

Depression can include sadness, apathy, guilt and despair. According to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), up to 15 percent of those with bipolar disorder commit suicide.

Between episodes, there is usually a period of normal mood.

Mania and depression do not necessarily alternate. A manic period may be followed by another manic period, or there may be a series of depressive episodes.

A large number of artists, leaders and celebrities have been diagnosed with bipolar disorder, including Carrie Fisher, Patty Duke and Winston Churchill. Some think the condition may go hand in hand with creativity.

Treatment with mood stabilizers, such as lithium and certain anticonvulsants, can be highly effective. Other medications may also be used. A growing community, though, sees the extremes of bipolar disorder as "mad gifts," not symptoms requiring treatment. One such group is the Icarus Project.

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Take a bipolar screening quiz online at PsychCentral.com.