Antidepressant treatment-emergent affective switch in bipolar disorder: a prospective case-control study of outcome.

Objective: Treatment-emergent affective switch has been associated to cycle acceleration and poorer outcome, but there are few studies addressing this issue. The aim of this study was to prospectively compare the outcome of patients presenting treatment-emergent affective switch with patients with spontaneous mania, regarding presence and polarity of a new episode and time to relapse.
Method: Twenty-four patients with bipolar disorder according to the DSM-IV were followed for 12 months. Twelve patients had treatment-emergent affective switch and twelve had spontaneous mania. Patients were evaluated weekly with the Young Mania Rating Scale and the Hamilton Depression Scale until remission of the index episode, and monthly until completion of the 12-month follow-up.
Results: Eleven patients with treatment-emergent affective switch had a recurrence on follow-up, all of them with major depressive episodes. In the group with spontaneous mania, six patients had a recurrence: two had a depressive episode, and four had a manic episode (p = 0.069 for new episode, p = 0.006 for polarity of the episode). Patients with treatment-emergent affective switch relapsed in a shorter period than patients with spontaneous mania (p = 0.016).
Conclusions: In this first prospective study, treatment-emergent affective switch patients were at greater risk of relapses, especially depressive episodes, and presented a shorter duration of remission when compared with patients with spontaneous mania.