Initial severity of major depression and efficacy of new generation antidepressants: individual participant data meta-analysis

Objective: The role of baseline severity as effect modifier in various psychiatric disorders is a topic of controversy and of clinical import. This study aims to examine whether baseline severity modifies the efficacy of various antidepressants for major depression through individual participant data (IPD) meta-analysis. Method: We identified all placebo-controlled, double-blind randomised trials of new generation antidepressants in the acute phase treatment of major depression conducted in Japan and requested their IPD through the public-private partnerships (PPPs) between the relevant academic societies and the pharmaceutical companies. The effect modification by baseline depression severity was examined through six increasingly complex competing mixed-effects models for repeated measures. Results: We identified eleven eligible trials and obtained IPD from six, which compared duloxetine, escitalopram, mirtazapine, paroxetine or bupropion against placebo (total n = 2464). The best-fitting model revealed that the interaction between baseline severity and treatment was not statistically significant (coefficient = -0.04, 95% confidence interval: -0.16 to 0.08, P = 0.49). Several sensitivity analyses confirmed the robustness of the findings. Conclusion: We may expect as much benefit from antidepressant treatments for mild, moderate or severe major depression. Clinical practice guidelines will need to take these findings into consideration.