Melancholic depression and response to quetiapine: A pooled analysis of four randomized placebo-controlled trials.

Background: Melancholic depression may preferentially respond to certain treatments. This study examined the efficacy of extended-release quetiapine monotherapy in patients with melancholic and nonmelancholic major depressive disorder.

Methods: Data from four randomized placebo-controlled trials was pooled. Melancholic features were assessed with baseline depression scale items according to DSM criteria. The outcome measure was response on the Montgomery-Åsberg Depression Rating Scale. Cox regression models predicting response over time with interactions between treatment condition and melancholic status were used to test for treatment effect heterogeneity.

Results: The 6-week response rate difference between quetiapine and placebo was roughly 10% greater in the melancholic subgroup, primarily due to a lower placebo response, although the subgroup-treatment interactions did not reach statistical significance. The main effect of quetiapine was significant in every model.

Limitations: The main limitations were the retrospective analysis and the post-hoc designation of melancholic depression based on scale items not designed for that purpose. Results should be considered preliminary and exploratory until replicated.

Conclusions: The lower placebo response rate in the melancholic subgroup is consistent with past research and reinforces the benefit of pharmacotherapy for these patients.