Mania is often characterized by euphoria, hypersexuality, hyperactivity, insomnia, intense productivity, hyper-imagination, a "flight of ideas," over-talkativeness, and sometimes agitation and even psychosis. Some persons with bipolar disorder may want to feel manic or hypomanic, cherishing the feelings of elation and energization associated with those phases (some use this as a reason to refuse medication). However, people in manic phases often exhibit impulsive, destructive, and irrational behavior which they later regret; and some manic patients report feeling extremely distressed and agitated and sometimes become paranoid or even hear voices.
Depression or clinical depression is often characterized by profound sadness and/or anxiety, slowness to conceive ideas and move, sleep disruptions, even suicidal thoughts or actions.
It should be noted that the mood swings of Borderline Personality Disorder (rapid mood shifts, multiple times a day for months and years; shifting between happiness and anger/depression depending of whether they get their way in situations; manipulative threats of, and dramatic displays of suicidal gestures; and acts of self injury) are not typical characteristics of Bipolar Disorder, although some have conjectured that the two conditions are related.
Bipolar disorder was originally believed to be a different form of but the same disorder as unipolar depression, but they are now widely regarded as two different disorders, both symptomatically and biochemically. (In fact, some scientists believe bipolar disorder is actually more closely related to schizophrenia than clinical depression.) In addition, while unipolar depression often occurs as a single episode (i.e. a person is only clinically depressed for one period in their life), bipolar disorder is typically a life-long condition, requiring long-term maintenance treatment.
Note on usage: "Manic-depression" was the original term used for the disorder. While it is still commonly used to refer to bipolar disorder, the term manic depression is now sometimes used by doctors to refer to the entire clinical spectrum of mood disorders that includes both bipolar disorder and unipolar depression. Others are trying to phase out the term entirely.
