The focus of this application is on the impact of providing depressed Veterans and their providers with the results of pharmacogenetic (PGx) testing for psychotropic medications. The project focuses on whether and how patients and providers use genetic test results given to them at the time an antidepressant is to be initiated to treat Major Depressive Disorder (MDD) and whether use of the test results improves patient outcomes. MDD is one of the most common conditions associated with military service and combat exposure, increases suicide risk, and worsens the course of common medical conditions, making it a leading cause of functional impairment and mortality. Validation of a PGx test to personalize the treatment of MDD represents an important opportunity to improve the healthcare of Veterans.