On CrazyBoards, the support and education boards I help moderate, people with bipolar disorder who rapid cycle are pretty common. Rapid cycling refers to having four or more distinct mood episodes a year, although usually what people are referring to on CB is more frequent. This may reflect who winds up on support boards or may reflect actual distribution, I don’t know right now.
It looks like almost always, rather than being a type of bipolar or a set pattern that’s persistent throughout the lifetime, rapid cycling is transient. It may or may not be a result of kindling (untreated mood episodes getting worse over time). We’ve known this for a long time, even if it isn’t widely known among patients: the studies referenced here (Goodwin and Jamison again) mostly range from late 1908s to mid-1990s.
Some additional things I’m wondering about:
If rapid cycling isn’t a type of bipolar disorder, is degree of variation in cycle lengths? For example, some people have a classic pattern consisting of a mania in the spring and a depression in the fall, and don’t deviate. But other people might sometimes have years between episodes and sometimes days between episodes.
If rapid-cycling is a result of kindling, and rapid-cycling is transient, does that mean people are getting kindled and later unkindled? Spontaneously, or due to medication, or both?