Bipolar disorder, also known as manic-depressive illness, is a brain disorder that causes unusual shifts in mood, energy, activity levels, and the ability to carry out day-to-day tasks. These shifts are different from the normal ups and downs that everyone goes through from time to time and they may have nothing to do with what is going on in someone's life.

Bipolar disorder is an episodic, or recurring disorder that typically consists of three states:

- a high state, called "mania
- a low state, called "depression"
- a well state, during which many people feel normal and function well.

The recurring and states of mania and depression (the symptoms of bipolar), and the mood swings between those states, can result in damaged relationships, poor job or school performance, and even suicide. But bipolar disorder can be treated, and people with this illness can lead full and productive lives.

Bipolar disorder is not easy to spot when it starts. The symptoms may seem like separate problems and not be recognized as parts of a larger problem. Some people suffer for years before they are properly diagnosed and treated. Like diabetes or heart disease, bipolar disorder is a long-term illness that must be carefully managed throughout a person's life.

Types of Bipolar Disorder

Doctors usually diagnose mental disorders using guidelines from the Diagnostic and Statistical Manual of Mental Disorders, or DSM. According to the DSM, there are four basic types of bipolar disorder:

   1. Bipolar I Disorder is mainly defined by manic or mixed episodes that last at least seven days, or by manic symptoms that are so severe that the person needs immediate hospital care. Usually, the person also has depressive episodes, typically lasting at least two weeks. The symptoms of mania or depression must be a major change from the person's normal behavior.

   2. Bipolar II Disorder is defined by a pattern of depressive episodes shifting back and forth with hypomanic episodes, but no full-blown manic or mixed episodes.

   3. Bipolar Disorder Not Otherwise Specified (BP-NOS) is diagnosed when a person has symptoms of the illness that do not meet diagnostic criteria for either bipolar I or II. The symptoms may not last long enough, or the person may have too few symptoms, to be diagnosed with bipolar I or II. However, the symptoms are clearly out of the person's normal range of behavior.

   4. Cyclothymic Disorder, or Cyclothymia, is a mild form of bipolar disorder. People who have cyclothymia have episodes of hypomania that shift back and forth with mild depression for at least two years. However, the symptoms do not meet the diagnostic requirements for any other type of bipolar disorder.

How Common is Bipolar Disorder?

Bipolar disorder affects about one to two percent of the adult population world wide.  Men and women are affected equally.

When Does Bipolar Disorder Start?

Bipolar disorder often develops in a person's late teens or early adult years. At least half of all cases start before age 25.  Some people have their first symptoms during childhood, while others may develop symptoms late in life.