With bipolar I disorder, moods swing between mania and depression, sometimes with periods of normal mood between extremes. All children with this disorder have episodes of mania, but episodes of depression vary. For example, some children do experience depression, and others rarely are depressed.
With bipolar II disorder, depression is more severe than mania. And manic episodes may last for fewer days and be less intense.
With cyclothymia, the high and low mood swings are not as severe as the mania and depression seen in bipolar I or bipolar II disorders.
Bipolar, NOS (not otherwise specified), is diagnosed when symptoms of mania and depression are not frequent or severe enough for the above diagnoses.
Rapid-cycling means that there have been at least four shifts between depression and mania over the past 12 months. These shifts occur quickly, sometimes within the same day. Often the shifts happen without a return to a normal mood in between the extremes.
Mixed-cycling (also known as mixed-features) means that symptoms of both mania and depression occur at the same time.