Comparative effectiveness of repeated ketamine infusions in treating anhedonia in bipolar and unipolar depression.

Objectives: Anhedonia is a common, persistent, and disabling phenomenon in patients with major depressive disorder (MDD) and bipolar depression (BD). This study was conducted to investigate the comparative effectiveness of repeated ketamine infusions in treating anhedonia in Chinese individuals suffering from MDD and BD.

Methods: Ninety-seven individuals suffering from MDD (n=77) or BD (n=20) were treated with six intravenous infusions of ketamine (0.5 mg/kg) administered over 40 min. Anhedonia was measured through the Montgomery-Åsberg Depression Rating Scale (MADRS). The antianhedonic response and remission were defined as ≥ 50% and ≥ 75% reduction in MADRS anhedonia subscale score one day after the sixth infusion, respectively.

Results: Anti-anhedonic response and remission rates after the sixth ketamine infusion were 48.5% (95% confidence interval=38.3-58.6) and 30.9% (95% confidence interval=21.6-40.3), respectively. When compared to baseline, a significant reduction in the MADRS anhedonia subscale score was observed at 4 h after the first infusion and was maintained with repeated infusions at any time point (all Ps<0.05). The anti-anhedonic effect of ketamine did not differ between the MDD and BD groups.

Conclusion: This preliminary study found that repeated ketamine infusions appeared to be effective at rapidly ameliorating anhedonia, with similar efficacy in MDD and BD.