Tonic Immobility and PTSD in a Large Community Sample

Abstract

People can be paralyzed when facing threat. Such paralysis, or peritraumatic “tonic immobility” (TI), is important as it seems associated with later PTSD development. However, the prevalence of TI is not known. This study investigated its prevalence in a large representative sample as well as its association with PTSD. 4781 participants from the general population completed measures of peritraumatic TI, peritraumatic fear, peritraumatic dissociation, trait anxiety, dissociative tendencies, behavioral inhibition, and PTSD symptoms. Extreme TI was rare in participants without PTSD (0.6% in those without trauma and 0.8% in those with trauma but without PTSD) but not in those with PTSD (7.6%). Moderate TI occurred more often (6.5%, 6.3% and 17.7% for participants without trauma, trauma without PTSD and trauma plus PTSD respectively). Extreme TI was more frequent in participants that experienced sexual violence, childhood emotional abuse, accidents and war-related traumas than in those that did not experience those traumas. In multivariate analyses TI, trait anxiety and dissociative tendencies predicted PTSD severity, with trait anxiety and TI being the most relevant predictors. These results stress the relevance of further exploration of TI responses.