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Harvard Medical School

Bipolar Disorder (Manic Depressive Illness or Manic Depression)

What Is It?

Bipolar disorder, which used to be called manic depressive illness or manic depression, is a mental disorder characterized by wide mood swings from high (manic) to low (depressed).

Periods of high or irritable mood are called manic episodes. The person becomes very active, but in a scattered and unproductive way, sometimes with painful or embarrassing consequences. Examples are spending more money than is wise or getting involved in sexual adventures that are regretted later. A person in a manic state is full of energy or very irritable, may sleep far less than normal, and may dream up grand plans that could never be carried out. The person may develop thinking that is out of step with reality -- psychotic symptoms -- such as false beliefs (delusions) or false perceptions (hallucinations). During manic periods, a person may run into trouble with the law. If a person has milder symptoms of mania and does not have psychotic symptoms, it is called "hypomania" or a hypomanic episode.

Bipolar disorder is now divided into two subtypes (bipolar I and bipolar II).

• Bipolar I disorder is the classic form where a person has had at least one manic episode.

• In bipolar II disorder, the person has never had a manic episode, but has had at least one hypomanic episode and at least one period of severe depression. Bipolar II disorder may be more common than Bipolar I.

A disorder that is classified separately, but is closely related to bipolar disorder, is cyclothymia. People with this disorder fluctuate between hypomania and mild or moderate depression without ever developing a full manic or depressive episode.

Some people with bipolar disorder switch frequently or rapidly between manic and depressive symptoms, a pattern that is often called "rapid cycling."

Most people who have manic episodes do also experience periods of depression. If manic and depressive symptoms overlap for a period, it is called a "mixed" episode. In some people, it may be difficult to tell which mood -- depression or mania -- is more prominent.

People who have had one manic episode most likely will have others if they do not seek treatment. The illness tends to run in families. Unlike depression, in which women are more frequently diagnosed, bipolar disorder happens nearly equally in men and women. Bipolar I and II disorders occur in up to 4% of the population.

Scientists are beginning to understand the biology of bipolar disorder better, although there is still much to learn. For example, people with bipolar disorder may have problems with their biological clock (or circadian rhythm). This discovery fits with our knowledge of bipolar disorder's effect on sleep -- less sleep during manic episodes, sleeping more than normal during depressive episodes.

Also, using advanced brain scanning techniques, scientists have found that people with bipolar disorder have a distinct pattern of activation in various brain regions (when compared to people without the disorder). Scientists are working hard to find the genes that put people more at risk for developing bipolar disorder. Discoveries in this area should help us distinguish the different subtypes of this disorder.

The most important risk of this illness is the risk of suicide. People who have bipolar disorder are also more likely to abuse alcohol or other substances.