The primary symptoms of bipolar disorder are dramatic and unpredictable mood swings.

Mania symptoms may include excessive happiness, excitement, irritability, restlessness, increased energy, less need for sleep, racing thoughts, high sex drive, and a tendency to make grand and unattainable plans.

Depression symptoms may include sadness, anxiety, irritability, loss of energy, uncontrollable crying, change in appetite causing weight loss or gain, increased need for sleep, difficulty making decisions, and thoughts of death or suicide.

There are several types of bipolar disorder; all involve episodes of depression and mania to a degree. They include bipolar I, bipolar II, cyclothymic disorder, mixed bipolar, and rapid-cycling bipolar disorder.

A person affected by bipolar I disorder has had at least one manic episode in his or her life. A manic episode is a period of abnormally elevated mood, accompanied by abnormal behavior that disrupts life.

Bipolar II is similar to bipolar I disorder, with moods cycling between high and low over time. However, in bipolar II disorder, the "up" moods never reach full-on mania.

In rapid cycling, a person with bipolar disorder experiences four or more episodes of mania or depression in one year. About 10% to 20% of people with bipolar disorder have rapid cycling.

In most forms of bipolar disorder, moods alternate between elevated and depressed over time. But with mixed bipolar disorder, a person experiences both mania and depression simultaneously or in rapid sequence.

Cyclothymia (cyclothymic disorder) is a relatively mild mood disorder. People with cyclothymic disorder have milder symptoms than in full-blown bipolar disorder.

Self-injury, often referred to as cutting, self-mutilation, or self-harm, is an injurious attempt to cope with overpowering negative emotions, such as extreme anger, anxiety, and frustration. It is usually repetitive, not a one-time act.

When a person's illness follows the classic pattern, diagnosing bipolar disorder is relatively easy. But bipolar disorder can be sneaky. Symptoms can defy the expected manic-depressive sequence.

Suicide is a very real risk for people with bipolar disorder, whether they're in a manic or depressive episode -- 10%-15% of people with bipolar disorder kill themselves. But treatment greatly lowers the risk.