We all experience a variety of moods such as happiness, sadness, and anger. Unpleasant moods and changes in mood are normal reactions in everyday life, and we can often identify the events that caused our mood to change. However, when we experience extreme mood changes that affect how we behave and function, these changes are often the result of a mood disorder.
Bipolar disorder (formerly known as manic-depressive disorder) is a mood disorder that consists of periods of extremely elevated mood (mania), extremely low mood (depression), and normal mood.
Bipolar disorder typically begins for people during adolescence and early adulthood. It is unusual for bipolar disorder to begin in childhood without strong familial risk factors, and it is rare for its onset to occur after the age of 60 (unless it is associated with another medical condition). Bipolar disorder occurs in about 2% of the adult population, and men and women are affected equally.
There is no single, proven cause of bipolar disorder, but research suggests that it is the result of abnormalities in the way some nerve cells in the brain function or communicate. Researchers also believe that there is a definite genetic link (family history) in which there is a higher risk for people who have a parent or full sibling (i.e., a first-degree relative) with bipolar disorder.
Whatever the precise nature of the cause of bipolar disorder, it clearly makes people with the disorder more vulnerable to emotional and physical stresses. As a result, upsetting life experiences, alcohol, illicit drug use, lack of sleep, or other stresses can trigger episodes of illness, even though these stresses do not actually cause the disorder.
Bipolar disorder is not the fault of the person suffering from it and is not the result of a "weak" or unstable personality. Rather, bipolar disorder is a treatable medical condition.