Introduction: Despite numerous explanatory hypotheses, few studies have involved a large national clinical sample examining risk factors in the occurrence of rapid cycling during the course of bipolar illness.
Methods: From 1,090 manic bipolar I disorder inpatients included in a multicenter national study in France, 958 could be classified as rapid or nonrapid cyclers and assessed for demographic, illness course, clinical, psychometric, temperament, comorbidity, and treatment characteristics.
Results: Rapid cycling bipolar disorder occurred in 9% (n=86) of the study group. Compared to nonrapid cyclers (n=872), patients with rapid cycling experienced the onset of their illness at a younger age, a higher number of prior episodes, more depression during the first episode, and more suicide attempts. At study entry, they also experienced manic episodes with more depressive and anxious symptoms, but less psychotic features. The following independent variables were associated with rapid cycling: longer duration of illness, antidepressant treatment, episodes with no free intervals, cyclothymic temperament, lower scores on the Scale for Assessment of Positive Symptoms and presence of thyroid disorder. Retrospective study limited to bipolar I disorder inpatients; several factors previously associated with rapid cycling were not assessed.
Conclusion: Our findings may confirm previous descriptions, according to which rapid cycling develops later in the course of illness following a sensitization process triggered by antidepressant use or thyroid dysfunction, in patients with a depression-mania-free interval course, and cyclothymic temperament.