bipolar disorder

n. manic-depressive psychosis, psychological illness characterized by extreme and sudden alternations between depression to euphoria (Psychology)

Bipolar disorder is a psychiatric condition defined as recurrent episodes of significant disturbance in mood. These disturbances can occur on a spectrum that ranges from debilitating depression to unbridled mania. Individuals suffering from bipolar disorder typically experience fluid states of mania, hypomania or what is referred to as a mixed state in conjunction with depressive episodes. These clinical states typically alternate with a normal range of mood. The disorder has been subdivided into bipolar I, bipolar II and cyclothymia, with both bipolar I and bipolar II potentially presenting with rapid cycling.
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Bipolar, or manic-depressive disorder, is a mood disorder that causes radical emotional changes and mood swings, from [more]Bipolar disorder - Community and Resources

Noun
1. a mental disorder characterized by episodes of mania and depression
(synonym) manic depression, manic depressive illness, manic-depressive psychosis
(hypernym) affective disorder, major affective disorder, emotional disorder, emotional disturbance
(hyponym) cyclothymia, cyclothymic disorder, cyclic disorder

Extreme mood swings punctuated by periods of generally even-keeled behavior characterize this disorder. Bipolar disorder tends to run in families. This disorder typically begins in the mid-twenties and continues throughout life. Without treatment, people who have bipolar disorder often go through devastating life events such as marital breakups, job loss, substance abuse, and suicide.