Original ArticlesThe Relation Between Posttraumatic Stress Symptom Severity and Startle Potentiation to Predictable and Unpredictable ThreatLieberman, Lynne MA*,†; Funkhouser, Carter J. MA*; Gorka, Stephanie M. PhD*,†; Liu, Huiting MA*; Correa, Kelly A. MA*; Berenz, Erin C. PhD*; Phan, K. Luan MD*,†,‡,§; Shankman, Stewart A. PhD*,†,∥Author Information Departments of *Psychology †Psychiatry ‡Anatomy and Cell Biology and the Graduate Program in Neuroscience, University of Illinois-Chicago §Jesse Brown VA Medical Center, Mental Health Service Line ∥Department of Psychiatry and Behavioral Sciences, Northwestern University, Chicago, Illinois. Send reprint requests to Stewart A. Shankman, PhD, Department of Psychiatry and Behavioral Sciences, Northwestern University, 680 N Lake Shore, Room 15-032, Chicago, IL 60611. E-mail: firstname.lastname@example.org. Sources of funding: National Institute of Mental Health grants awarded to Dr Shankman and Dr Phan (R01 MH098093, primary investigator: Dr Shankman; and R01 MH101497, primary investigator: Dr Phan). The Journal of Nervous and Mental Disease: May 2020 - Volume 208 - Issue 5 - p 397-402 doi: 10.1097/NMD.0000000000001138 Buy Metrics Abstract Aberrant threat reactivity has been implicated in the pathophysiology of posttraumatic stress disorder (PTSD); however, the literature on this association is mixed. One factor that may contribute to this inconsistent association is differences in severity of posttraumatic stress symptoms (PTSSs) across studies, but no studies have tested this hypothesis. The relation between PTSD and threat reactivity may also differ between unpredictable threats (U-threats) and predictable threats (P-threats), given burgeoning evidence to support a particular role for aberrant responding to U-threat in PTSD. The present study examined how PTSS severity relates to startle potentiation to U-threat and P-threat in a trauma-exposed community sample (N = 258). There was a negative linear, but not quadratic, relation between PTSS severity and startle potentiation to U-threat, but not P-threat. Blunted defensive responding to U-threat may therefore contribute to higher levels of PTSSs and may represent a novel treatment target for higher levels of PTSSs. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.