VOL. 6, NO. 12 THE AMERICAN JOURNAL OF MANAGED CARE 1327 . . . PATIENT OUTCOMES . . . Determinants of Antidepressant Treatment Outcome Neeraj Sood, MS; Michael Treglia, PhD; Robert L. Obenchain, PhD; Brian Dulisse, PhD; Catherine A. Melfi, PhD; and Thomas W. Croghan, MD D espite significant advances in depression therapy, considerable variability remains in treatment outcomes. For instance, depressive disorders are associated with high rates of relapse and recurrence during a patient’s lifetime. The National Institute of Mental Health consensus con- ference on relapse and recurrence of depression found that 50% to 85% of people who have an episode of major depression experience a recurrent episode during their lifetime. Of these, 50% will experience recurrence within 2 years of the initial episode. 1 episode of antidepressant therapy, (2) suicide attempt, (3) psychiatric hospitalization, (4) mental health–related emergency department visits, or (5) electroconvulsive therapy. Antidepressant use pat- terns were used to construct a measure for adher- ence to treatment guidelines. Multivariate Cox pro- portional hazard and logit regression models were used to predict relapse/recurrence and adherence with treatment guidelines, respectively, for each patient. Results: Factors that affect relapse/recurrence include comorbidities, demographics, and adher- ence to treatment guidelines. Factors that affect adherence to treatment guidelines include choice of initial antidepressant drug, comorbidities, psy- chotherapy, and frequency of physician visits. Conclusions: Adherence to treatment guidelines was associated with a significant reduction in the likelihood of relapse or recurrence of depression. Choice of initial antidepressant drug affects adher- ence to treatment guidelines. (Am J Manag Care 2000;6:1327-1336) Abstract Objective: To understand the determinants of the outcome of an episode of major depression, includ- ing factors that affect receipt of guideline-consistent care and their subsequent effect on treatment out- comes, particularly relapse or recurrence. Results of previous studies are generalized to a population typ- ical of depressed individuals in the United States, ie, a cohort of antidepressant users with employer-pro- vided health benefits. Study Design: A quasi-experimental design was used to assess the determinants of the outcome of an episode of major depression. Healthcare utiliza- tion–based measures of treatment characteristics and outcomes were used. Patients and Methods: The final analytical file for this study contained data on 2917 patients who had an antidepressant prescription associated with an indicator of a depressive disorder. We identified relapse or recurrence of depression by (1) a new From the Department of Economics, Indiana University Purdue University at Indianapolis (NS); the Health Outcomes Evaluation Group (NS, CAM, TWC), Global Health Outcomes Research (MT), and Statistics and Mathematical Sciences (RLO, BD), Eli Lilly and Co, Indianapolis; the School of Medicine (RLO, CAM, TWC), the Regenstrief Institute for Health Care (CAM, TWC), and the Bowen Research Center (TWC), Indiana University, Indianapolis; and the School of Public and Environmental Affairs, Indiana University, Bloomington (TWC). This work was presented in part at the annual meeting of the Academy of Managed Care Pharmacy, Atlanta, GA, October 7, 1999. This study was funded by Eli Lilly and Co, Indianapolis, IN. Address correspondence to: Thomas W. Croghan, MD, Health Outcomes Evaluation Group, Drop Code 1850, Eli Lilly and Co, Indianapolis, IN 46285. E-mail: croghan_thomas_w@lilly.com.