[Unipolar mania: a distinct entity or characteristic of manic preponderance?]

It has been reported that fewer patients with unipolar mania respond to lithium prophylaxis as do those with classical bipolar disorder. This study aimed to determine if the difference to response to lithium is related to unipolar mania or to a high preponderance of mania during the course of bipolarity.

The study included bipolar-I patients (according to DSM-IV criteria) that had a ≥ 2-year history of either lithium or valproate prophylaxis as monotherapy. The response rate in the patients with unipolar mania and classical bipolar disorder were compared. Then, the response rate to lithium in all the patients with a manic episode rate <50% and >50%, and <80% and >80% during their course were compared. Finally, the above comparisons were repeated, excluding the patients with unipolar mania.

The study included 121 bipolar-I patients (34 unipolar mania and 87 classical bipolar disorder). The response rate to lithium prophylaxis was significantly lower in the unipolar mania group than that in the bipolar group, whereas, the response rate to valproate prophylaxis was similar in both groups. Additionally, significantly fewer patients with a manic episode rate >80% during their course responded to lithium, followed by those with a manic episode rate >50%; however, these differences disappeared when the unipolar mania group was excluded from the comparison.

Fewer patients with unipolar mania responded to lithium prophylaxis than those with classical bipolar disorder, which appeared to be related to unipolar mania, rather than to a high manic predominance during the disease course. On the other hand, response to valproate prophylaxis was similar in the unipolar mania and classical bipolar disorder groups.