Periodicity of episode occurrences in rapid cycling affective disorders

We analyzed the medical records of nine patients with severe rapid cycling affective disorders (RCAD), and determined the cycle of mania occurrences by calculating the period between two successive onsets of mania for each patient. Using the cycle as the index we devised a cycle-oriented diagram by dividing the observation period by the index cycle, and visually studied the mode of episode occurrences. In seven patients, the onset of mania generally followed the index cycle, but sometimes shifted from the day estimated by the index cycle. The shift seemed to be caused by a cycle other than the index cycle, which appeared temporarily in the course. The period between two successive onsets of mania was often several times longer than the index cycle length. In patients with RCAD, some sort of periodic rhythms may possibly control the course of episode occurrences on a continuing basis.