(depressive illness.) A form of bipolar illness, this is a mood rollercoaster. A person may feel up one day and down the next, or up one week and down the next in seemingly unpredictable patterns. Periods of normal mood may be few and far between. Hypomanias occur, along with mild depressions.
Cyclothymia is a chronic, but less extreme, form of bipolar disorder that consists of short periods of mild depression alternating with short periods of hypomania. The onset of each phase is separated by short periods of normal mood. This diagnosis is excluded if the patient has had either a manic episode or a major depressive episode.