Pharmacologic treatments for major depressive disorder (MDD) have long focused on monoamine mechanisms, with the early success of tricyclic and MAOI antidepressants, and marked by the advent of selective serotonin reuptake inhibitors (SSRIs). Despite these advances, the failure rate for any specific treatment imposes formidable delays in relief from depression in patients for whom hopelessness and discouragement are already a concern. Without objective tests indicating the likelihood of an individual’s response to treatment, the risks to the patient grow with each failure. A reliable, objective, and readily available measure capable of differentiating between those who may or may not respond to specific treatments would find a much-needed place in clinical practice.
