Second-generation antipsychotics show higher response rates than placebo for augmenting major depressive disorderAntipsychotics show promise in treating major depressive disorder

This meta-analysis evaluated the efficacy of pharmacological augmentation strategies for patients with major depressive disorder (MDD). The study included a large aggregate population of 13,616 adults diagnosed with MDD to assess three primary classes of augmenting agents: lithium, triiodothyronine (T3), and second-generation antipsychotics (SGAs). The primary outcome measured was the response rate, defined as a reduction in depressive symptoms of at least 50%.

The intervention groups included lithium, T3, and various SGAs including aripiprazole, quetiapine, brexpiprazole, and cariprazine. These were compared against placebo controls to determine the magnitude of effect for each augmentation strategy. The study specifically utilized different statistical modeling techniques, including conventional meta-analysis, Two-Stage Availability (TSA), PET-PEESE, and selection models, to refine the evidence for lithium and other agents.

Regarding SGAs, the analysis reported a statistically significant higher response rate than placebo with an odds ratio (OR) of 1.53 (95% CI: 1.42-1.65; I^2=0%). Specifically, aripiprazole, quetiapine, brexpiprozole, and cariprazine were identified as having TSA-supported efficacy. In contrast, the results for lithium were more complex. A conventional meta-analysis of 17 studies showed a benefit with an OR of 2.06 (95% CI: 1.30-3.27; I^2=11.5%). However, this finding was not supported by TSA analysis. Furthermore, lithium results were reported as statistically non-significant when analyzed using PET-PEESE and selection models. The evidence for T3 augmentation did not show a significant advantage over controls, with an OR of 1.19 (95% CI: 0.53-2.70) based on 6 studies.

Safety and tolerability data, including specific adverse event rates or discontinuation figures, were not reported in the included data for this analysis. Consequently, the relative tolerability of these agents cannot be quantified from this specific evidence set.

These results provide a nuanced view of augmentation options. While lithium has shown benefit in conventional meta-analyses, its efficacy is not supported by more rigorous TSA models. T3 did not show significant advantage over controls. The findings suggest that SGAs with TSA-supported benefits, specifically aripiprazole, quetiapine, brexpiprozole, and cariprazine, may be prioritized in clinical practice for MDD augmentation.

Several methodological limitations were noted. The evidence for T3 was described as sparse. Furthermore, the findings regarding lithium are constrained by the fact that many included trials were conducted before modern operational definitions of treatment-resistant depression were established. These factors contribute to a limited certainty of evidence for both lithium and T3 augmentation.

Clinically, these results suggest that when selecting an augmenting agent for MDD, clinicians may favor SGAs with robust TSA support. The lack of significant findings for T3 and the inconsistent results for lithium under advanced modeling suggest a need for more cautious interpretation of those specific options. Questions remain regarding the long-term tolerability of these agents and their efficacy in modern cohorts defined by current treatment-resistant criteria.