Oops, deleted what I wrote here earlier. This is for DSM V:

"According to the American Psychiatric Association's Diagnostic and Statistical Manual, Fifth Edition (DSM-5), the diagnostic criteria for rapid cycling are [2]:

●At least four bipolar mood episodes in a 12-month period
●The episodes meet both the symptom and duration criteria for major depression (table 3), mania (table 1), or hypomania (table 2); the episodes that occur as part of a rapid cycling pattern are no different from episodes that occur as part of a non-rapid cycling pattern. Mood episodes that are directly caused by substance intoxication (eg, cocaine or corticosteroids) or a general medical disorder do not count toward defining a rapid-cycling pattern.
●The mood episodes can occur in any order or combination
●The episodes are demarcated by either
---- •A period of partial or full remission for at least two months, or
---- •A switch to an episode of opposite polarity. Manic and hypomanic episodes are counted as being on the same pole; thus, a switch in polarity involves one of these episodes and an episode of major depression. The time frame for switching poles is less than two months between the point that the patient has remitted from a mood episode on one pole and the point that the patient becomes ill with an episode on the other pole. In some cases the switch occurs suddenly."

http://www.uptodate.com/contents/rap...-and-diagnosis