In this disorder, there is at least one episode of mania (hypomania; acute delirious mania) and one of depression (simple retardation or acute depression). A brief period of normality may be present between the two states, but in the majority of cases transition is direct. Aetiology unknown.
Jean Pierre Falret studied depression and suicide for 32 years, and what he noticed was that there were cycles of depression and cycles of elation. He realized that these cycles were part of another disease, different from simple depression. He also noticed that the disorder was "generally found in similar form in ascendants and descendants".
- J. P. Falret:
Mémoire sur la folie circulaire, forme de la maladie mentale caractérisée par la reproduction successive et régulière de l’état maniaque, de l’état mélancolique, et d’un intervalle lucide plus ou moins prolongé.
Bulletin de l'Académie impériale de médecine, Paris, 1854, 19: 382-400.