Bipolar I disorder involves periods of severe mood episodes from mania to depression.
Bipolar II disorder is a milder form of mood elevation, involving milder episodes of hypomania that alternate with periods of severe depression.
Cyclothymic disorder describes brief periods of hypomaniac symptoms alternating with brief periods of depressive symptoms that are not as extensive or as long-lasting as seen in full hypomanic episodes or full depressive episodes.
"Mixed features" refers to the occurrence of simultaneous symptoms of opposite mood polarities during manic, hypomanic or depressive episodes. It's marked by high energy, sleeplessness, and racing thoughts. At the same time, the person may feel hopeless, despairing, irritable, and suicidal.
Rapid-cycling is a term that describes having four or more mood episodes within a 12-month period. Episodes must last for some minimum number of days in order to be considered distinct episodes. Some people also experience changes in polarity from high to low or vice-versa within a single week, or even within a single day, meaning that the full symptom profile that defines distinct, separate episodes may not be present (for example, the person may not have a decreased need for sleep). Sometimes called "ultra-rapid" cycling, there is debate within psychiatry as to whether this phenomenon is a valid or well-established feature in bipolar disorder. A pattern of rapid cycling can occur at any time in the course of illness, although some researchers believe that it may be more common at later points in the lifetime duration of illness. Women appear more likely than men to have rapid cycling. A rapid-cycling pattern increases risk for severe depression and suicide attempts. Antidepressants may sometimes be associated with triggering or prolonging periods of rapid cycling. However, that theory is controversial and is still being studied.