Background: Cyclicity is the essential feature of Bipolar disorder, but the effect of different
cycle patterns on the clinical features is poorly understood. Moreover, no studies investigated the
relationship between mania and depression inside the manic-depressive cycle.
Objective: The aim of this study is to verify the presence of a relationship between the manic and the
depressive phase during the course of bipolar disorder.
Method: 160 consecutive patients with BD type I were recruited and followed for a mean period of 10
years. During the follow-up period, four types of euthymic phases were collected: free intervals present
between a depressive and a manic/hypomanic episode (D-M); free intervals present between a
manic/hypomanic and a depressive episode (M-D); free intervals present between two depressive
episodes (D-D); free intervals present between two manic/hypomanic episodes (M-M). One-way
ANOVA using the groups as independent variable and the duration of the free intervals as dependent
variables was used. Furthermore, ANOVA was followed by Fisher's Protected Least Significant
Difference post-hoc test to measure between-group differences.
Results: M-D-free interval phases were shorter than D-M-free intervals. M-D intervals were the shortest
ones, the D-D and D-M did not differ, and the M-M were the longest.
Conclusion: The strict temporal link between manic and depressive phases supports the idea that the
manic-depressive cycle usually begins with a manic episode, and that the subsequent depression is often
the consequence of subsiding mania.