Similarly, depression as a disease can be much more than mere sadness.
Affected individuals have periodic attacks during which they shift from one mood pole to the other.
The severity of the disorder varies widely. But severely affected individuals are mentally ill. They cannot cope with the demands of ordinary life, especially when they are going through periods of depression. Aside from the toll it takes in misery during depression and from impulsive acts during mania, bipolar disorder frequently leads to suicide, often as the patient passes from a depressive stage into mania. Cause The basic cause of bipolar disorder is unknown, although it seems to involve the chemicals that transmit messages from one nerve to another.