Bipolar

A mental disorder marked by alternating periods of deep depression and extreme euphoria (mania). Contrary to popular belief, the violent mood swings associated with this illness are far more prolonged than ordinary emotional ups and downs, and the shifts of mood are sustained, lasting weeks, months or even years. The classic form of this condition is an extremely severe form of psychiatric disease but in more recent times milder variations more depressive-heavy and less manic have been included. It, however, remains very serious in all its forms and no group of people, mentally ill or mentally healthy, commit suicide half as much as manic-depressives do. It's a horrible disease and certainly not to be trivialised as just "mood swings".