The role of tonic immobility during re-experiencing trauma in PTSD treatment

Tonic immobility (TI) is a profound paralysis that may occur during extreme stress. Previous studies have found that TI during trauma was associated with poorer recovery from posttraumatic stress disorder (PTSD). Importantly, TI can re-occur during re-experiencing the trauma (TIre-exp). It is unclear whether TIre-exp also hinders recovery from PTSD or declines along with other PTSD symptoms after treatment. We examined whether pre-treatment self-reported TIre-exp would predict PTSD symptoms after trauma-focused treatment, including related constructs as depression and dissociation. and investigated pre- to post-treatment changes in TIre-exp. We also explored individual differences in TIre-exp course. A total of 257 patients with PTSD, referred to a clinic for intensive trauma-focused therapy, completed measures for PTSD symptoms and TIre-exp at pre- and posttreatment, and potential confounding variables (dissociative tendencies, somatoform dissociation, dissociative subtype, and depression) at pre-treatment. Higher pre-treatment TIre-exp predicted elevated post-treatment PTSD symptoms, but not after controlling for potentially confounding constructs. Overall, TIre-exp decreased from pre- to post-treatment, and a greater decrease in TIre-exp was associated with a greater decrease in PTSD symptoms. However, four distinct clusters could be identified, which differed in TIre-exp course: High-stable, High-decrease, Moderate and Low TIre-exp. End-state was worse for patients in the High-stable and Moderate clusters. Thus, in the general sample, pre-treatment TIre-exp was not associated with reduced recovery, and TIre-exp generally decreased after treatment, suggesting that TIre-exp may be related to the PTSD symptomatology, responding well to trauma-focused CBT treatment. However, TIre-exp may not decline in specific patient groups. Future research may address how TIre-exp can be targeted for these patients.