Journal of Personality Disorders, 33, 2019, 429 © 2019 The Guilford Press 1 From Johns Hopkins University School of Medicine, Baltimore, Maryland (M. K., R. K. B., J. P., J. G., J.-M. L.); and University of Maryland School of Medicine, Baltimore, Maryland (S. S.). We gratefully acknowledge the clinical staff at Addiction Treatment Services for their contributions to this research. We also acknowledge Haijuan Yan, MS, for her assistance in conducting the statistical analyses. Finally, we acknowledge and thank the research staff whose diligence helped ensure the quality and in- tegrity of the study, especially Kori Kindbom, MA, Jim Blucher, MA, Rachel Burns, BA, Jennifer Mucha, MA, and Michael Sklar, MA. The authors report no fnancial relationships with commercial interests. This study was supported by research grant RC1 DA028154 (M. Kidorf, PI) from the National Institute on Drug Abuse. Address correspondence Michael Kidorf, PhD, Addiction Treatment Services – BBRC, Johns Hopkins Bay- view Medical Center, 5510 Nathan Shock Dr., Suite 1500, Baltimore, MD 21224. E-mail: mkidorf@jhmi.edu IMPACT OF PERSONALITY DISORDER ON THE TREATMENT OF PSYCHIATRIC DISORDERS IN PEOPLE RECEIVING METHADONE-ASSISTED TREATMENT Michael Kidorf, PhD, Stephanie Salazzo, MD, Robert K. Brooner, PhD, Jessica Peirce, PhD, Jim Gandotra, MD, and Jeannie-Marie Leoutsakos, PhD This study evaluates personality disorder as a moderator of psychiatric treatment response in people receiving methadone-assisted treatment. Participants (N = 125) were enrolled in a 12-week parent study that evaluated the impact of incentives on attendance to psychiatric care. All participants had a current DSM IV-R Axis I disorder and were classifed based on presence of an Axis II disorder: Axis I-only (n = 46) versus Axis I + II (n = 79). All participants received an identical protocol of psychiatric and substance use disorder care. Although Axis I + II participants endorsed more psychiatric distress (on the Hopkins Symptom Checklist–Revised) throughout treatment, they reported signifcant reductions in distress that paralleled reductions reported by Axis I-only participants. Rates of substance use were low and similar across groups. Results support the benefts of integrated psychiatric and substance use care for people with opioid use disorder, with or without a co-occurring personality disorder. Keywords: integrated care, methadone-assisted treatment, personality disorder, treatment response, substance use More than 2.5 million people in the United States have opioid use disorder (Center for Behavioral Health Statistics and Quality, 2015). People seeking treatment for opioid use disorder have a much higher prevalence of mood and