The prognostic significance of "switching" in patients with bipolar disorder: a 10-year prospective follow-up study.

Objective: This study explored whether "switching" (i.e., the direct transition from one mood polarity to the other) has significant prognostic implications in patients with bipolar disorder.
Method: Bipolar disorder patients (N=97) whose first prospectively observed episode included at least one mood polarity switch and 97 bipolar disorder patients whose index episode was monophasic were compared with respect to several demographic and historical variables, symptomatic features of the index episode, time to recovery from the index episode, time spent in an affective episode during a prospective observation period, and psychopathological and psychosocial outcome at a 10-year follow-up interview.
Results: Patients whose index episode included at least two mood polarity switches spent significantly more time in an affective episode during the observation period and had a significantly worse psychopathological and psychosocial outcome 10 years after recruitment than those whose index episode included only one mood polarity switch or was monophasic. Patients whose polyphasic index episode started with depression spent a significantly higher proportion of time in an affective episode and had a significantly worse 10-year outcome than those whose polyphasic index episode started with mania or hypomania. Retention of the switching pattern throughout the observation period was seen in 42.4% of patients whose index episode started with mania and in 65.2% of those whose index episode started with depression.
Conclusions: An index episode including at least two mood polarity switches, especially if starting with depression, is associated with a poor long-term outcome in patients with bipolar disorder. This pattern represents a significant target for new pharmacological and psychosocial treatment strategies.