(PS11-A19) Tonic Immobility and Posttraumatic Stress: The Role of Threat Interpretation Bias

Tonic immobility (TI) is a common defensive response to threat, with prevalence estimates in traumatic situations ranging from 30 to 70%. TI involves temporary paralysis or “freeze” accompanied by fear and dissociation. Research suggests that TI is associated with increased rates of posttraumatic stress disorder (PTSD), symptom severity, and treatment resistance. In order to improve outcomes for individuals who experience TI during their trauma, we must seek to understand the mechanisms of this relationship. While some work suggests TI may result in alterations to threat perception and processing, current research on mechanisms of the relationship between TI and PTSD is limited to examining the role of emotions (e.g., guilt, shame). Therefore, the current study examines the relationships between TI experience, threat interpretation bias (i.e., the tendency to perceive ambiguous stimuli as threatening), and PTSD symptoms. Participants (N = 111) were recruited as part of an experimental study examining defensive responses in threatening scenarios. Participants completed a battery of self-report questionnaires including demographics, lifetime traumatic event exposure (LEC-5), TI experience (TIQ-R), threat interpretation bias (TS), and posttraumatic stress symptoms (PCL-5). Multiple linear regression analyses and an SPSS PROCESS mediation model were run to examine the relationships between TI, threat interpretation bias, and PTSD symptoms. Results demonstrated effects of TI experience on threat interpretation bias (t = 2.83, β = .36, p = .007) and PTSD symptoms (t = 3.39, β = .34, p = .001), after controlling for lifetime trauma exposure. Further, results from mediation analyses demonstrated that interpretation bias mediates the relationship between TI experience and PTSD symptoms (indirect effect: β = .31, 95%CI [.07, .62]. These results provide initial evidence for the role of threat interpretation bias in the relationship between TI experience and PTSD symptoms. Broadly, interpretation bias is a well-established, modifiable risk factor for psychopathology and research suggests that interpretation bias modification (CBM-I) interventions are effective in reducing mood and anxiety symptoms. Thus, future work should examine the use of CBM-I for threat among individuals endorsing TI experience and PTSD symptoms. The addition of threat related bias modification to current evidence-based treatments may have the potential to improve outcomes among individuals who have experienced TI.