Bipolar disorder is a severe mental illness. People who suffer from it experience unusual mood changes. They can go from being very active and happy to feeling very sad and hopeless. And, well, start the cycle again. They often have normal moods between one cycle and another. The sensations of euphoria and activity are called manias. Those of sadness and despair are called depression.
The causes of this disorder are not entirely clear. They can be genetic, so they can have a family tendency. Another cause may be an abnormal structure of brain functions.
Bipolar disorder usually begins in the late teens or early adulthood but children and adults may also suffer from it. Illness, generally, lasts a lifetime.
If left untreated, bipolar disorder can damage personal relationships, cause poor performance at school or at work and even suicide. However, there are effective treatments to treat the symptoms: medicines and "talk therapy". The combination of both is usually what works best. 