The goal of this phased FOA (either R33/R61 or UG3/UH3) is to accelerate the development of sensitive biomarkers/tools to predict individual treatment-response between two or more existing treatments for depression. In phase 1 (up to 2 years) preliminary studies (e.g., retrospective secondary analyses of data from completed clinical trials and/or in nimble, fast-fail pilot studies) will de-risk the test technology demonstrating that there is enough signal for clinical utility (futility analyses, ROC curves, and/or effect size will be evaluated as go/no-go criteria). Phase 2 (up to 5 years) innovators will prospectively test the efficacy of the biomarker/tool in large-scale biomarker/tool-stratified clinical trials with the goal of beating standard-of-care decision-making (i.e., clinician/patient treatment assignment will be the CTRL group vs the test).