The impact of tonic immobility reaction on the prognosis of posttraumatic stress disorder.

Tonic immobility is the last defense reaction to entrapment by a predator. In humans, peritraumatic tonic immobility was correlated with PTSD severity and poor response to treatment. This study compared the role of peritraumatic dissociation, panic physical symptoms and tonic immobility as predictors of response to standard pharmacotherapy for PTSD. Thirty-six PTSD patients underwent a naturalistic pharmacological treatment. The Posttraumatic Stress Disorder Checklist - Civilian Version (PCL-C) and the Clinical Global Impressions Severity of Illness item scores (CGI-S) were employed at baseline and endpoint to examine treatment outcome. Peritraumatic reactions were assessed using the Physical Reactions Subscale, the Peritraumatic Dissociative Experiences Questionnaire and four motor questions of the Tonic Immobility Scale. After controlling for confounders, tonic immobility was the best predictor of a poor response to treatment, either considering the PCL-C or the CGI-S scores. Tonic immobility seems to have a greater negative impact on PTSD prognosis than peritraumatic panic or dissociation. Additional translational and clinical research may inform about particular mechanisms underlying tonic immobility and open new avenues for prevention and treatment of PTSD.

Peritraumatic tonic immobility predicts a poor response to pharmacological treatment in victims of urban violence with PTSD.

INTRODUCTION: Tonic immobility is the last defense against predation in animals and is characterized by paralysis and analgesia. In humans, it has only been reported in women victims of sexual abuse. OBJECTIVE: This study evaluated the prevalence of peritraumatic tonic immobility (PTI) in patients with PTSD and investigated its association with response to treatment. METHOD: Victims of urban violence with PTSD diagnosed through the SCID-IV (n=23) underwent a naturalistic pharmacological treatment according to the recommended guidelines for PTSD. The Post-Traumatic Stress Disorder Checklist--Civilian Version (PCL-C) and the Clinical Global Impressions (CGI) Severity scores were applied at baseline and endpoint. PTI was assessed using the Tonic Immobility Scale. RESULTS: PTI was reported by both genders in 43% of the sample. Patients with PTI responded significantly poorly to treatment than those without it, either considering the PCL-C or the CGI scores. LIMITATIONS: This study probed PTI retrospectively and was based on a small sample recruited in a tertiary clinic. CONCLUSIONS: We have expanded the scope of the two previous investigations on PTI by showing its occurrence also in men and during non-sexual violence. In addition, the finding of a significant relationship between PTI and poor response to treatment of PTSD indicates that PTI may carry a prognostic value in this disorder and suggests that PTI should be routinely assessed in traumatized patients.