Selecting the best treatment for subjects with resistance to an initial antidepressant poses a considerable challenge for clinicians. The most widely prescribed antidepressants usually require 4-6 weeks of therapeutic dosing before a marked clinical improvement in symptoms is observed. Therefore, determining the optimal regimen can take several weeks or months for subjects who are resistant to the first line antidepressant. A tool for predicting eventual clinical response to antidepressants could help inform and accelerate the process of identifying the most efficacious treatment option for a given subject.