The overall goal of the STAR*D trial, funded by the National Institute of Mental Health, was to assess the effectiveness of depression treatments in patients diagnosed with major depressive disorder, in both primary and specialty care settings. It is the largest and longest study ever conducted to evaluate depression treatment. Each of the four levels of the study tested a different medication or medication combination. The primary goal of each level was to determine if the treatment used during that level could adequately treat participants’ major depressive disorder (MDD). Those who did not become symptom-free could proceed to the next level of treatment.