Borderline Personality Features and Harmful Dysregulated Behavior: The Mediational Effect of Mindfulness Peggilee Wupperman, 1,2 Melissa Fickling, 3 David H. Klemanski, 4 Matthias Berking, 5 and Jeannie B. Whitman 6 1 John Jay College/City University of New York 2 Yale University School of Medicine 3 University of North Carolina at Greensboro 4 Yale University Department of Psychology 5 University of Marburg, Germany 6 University of Texas Southwestern Medical Center Objectives: The current preliminary study investigated whether deficits in mindfulness (awareness, attentiveness, and acceptance of the present experience) may underlie the relationship of borderline personality disorder (BPD) features to self-injury and overall acts of harmful dysregulated behavior. Method: Nonparametric bootstrapping procedures were used to examine theoretical relationships among variables in a psychiatric sample of adults (N = 70). Participants were asked to imagine them- selves in distress-inducing situations and then write what they would actually do to decrease distress in such situations. Results: As hypothesized, mindfulness statistically mediated the relationship of BPD features to reported acts of (a) self-injury and (b) overall harmful dysregulated behaviors. Conclusions: Difficulties in the ability to be aware, attentive, and accepting of ongoing experience may play a role in the relationship of BPD features to harmful dysregulated behaviors. Future research should clarify potential reciprocal effects between BPD features and mindfulness with prospective, multioccasion designs. C  2013 Wiley Periodicals, Inc. J. Clin. Psychol. 00:1–9, 2013. Keywords: mindfulness; dysregulation; borderline personality; self-injury; impulsivity; substance Borderline personality disorder (BPD) is characterized by pervasive instability in emotions, interpersonal relationships, and identity, as well as severe and harmful dysregulated behaviors (American Psychiatric Association, 2000). BPD features are associated with suicide attempts, nonsuicidal self-injury, substance abuse, physical aggression, disordered eating, and a host of other dysregulated behaviors that can cause harm to the individual and the individual’s fam- ily (American Psychiatric Association, 2000; Tragesser et al., 2010). These behaviors also have widespread societal costs, including chronic unemployment, auto accidents, frequent hospital- ization, and increased utilization of overall healthcare resources (e.g., Linehan & Heard, 1999; Paris, 1993; Zanarini, Frankenburg, Hennen, Reich, & Silk 2005). Of note is that much of the healthcare utilization results from the high rates of deliberate self-injury (i.e., nonsuicidal self-injury or suicide attempts). Among individuals who meet criteria for BPD, approximately 60%–80% engage in deliberate self-injury and 8%-10% die by suicide (American Psychiatric Association, 2000; Pompili, Girardi, Ruberto, & Tatarelli, 2005). Despite extensive research on harmful dysregulated behaviors in BPD, the constructs that account for these behaviors are not yet fully understood. We propose that BPD-related We thank the Donaghue Medical Research Foundation and Dr. Colon Ross for providing support. The authors also thank their skilled team of coders and research assistants, including Alisa Pisciotta, M.A., Monique DiNapoli, M.A., Kathryn James, M.A., Karina Koerner, Ph.D., Michal Yehezkal, M.A., Jennifer Varley, M.A., and Mia Gintoft, M.D. Please address correspondence to: Peggilee Wupperman, John Jay College/City University of New York, Psychology Department, Tenth Floor, 524 W 59 th St., New York, NY 10019. E-mail: pegwupp@hotmail.com JOURNAL OF CLINICAL PSYCHOLOGY, Vol. 00(00), 1–9 (2013) C  2013 Wiley Periodicals, Inc. Published online in Wiley Online Library (wileyonlinelibrary.com/journal/jclp). DOI: 10.1002/jclp.21969