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.