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.
The expert view of bipolar disorder will continue to evolve, but it is now commonly divided into two subtypes (bipolar I and bipolar II) based on the dividing line between mania and hypomania described above.
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 significant depression.
Most people who have manic episodes also experience periods of depression. In fact, there is some evidence that the depression phase is much more common than periods of mania in this illness. Bipolar depression can be much more distressing than mania and, because of the risk of suicide, is potentially more dangerous.
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." If manic and depressive symptoms overlap for a period, it is called a "mixed" episode. During such periods, 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.
Since bipolar disorder can come in so many forms, it is difficult to determine its prevalence. Depending on how they define the disorder, researchers estimate that bipolar disorder occurs in up to 4% of the population. When a particularly broad definition is used, the estimate can be even higher.
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.