Tonic immobility during re-experiencing the traumatic event in posttraumatic stress disorder.

Tonic Immobility (TI) is an evolved defence response, characterized by physical immobility. Peritraumatic TI has been linked to posttraumatic stress disorder (PTSD). However, samples sizes in clinical studies have been small, and little is known about TI reactions post trauma, for instance during trauma reminders. The prevalence of peritraumatic TI and TI during re-experiencing the traumatic event was examined by self-report in 184 patients with chronic PTSD. Moderate peritraumatic TI was reported by 26.6% of the participants (n = 49) and extreme peritraumatic TI by 52.2% (n = 96). During re-experiencing the traumatic event, 35.3% (n = 65) reported moderate TI, and 37.0% (n = 68) extreme TI. Peritraumatic TI was related to PTSD symptom severity and TI during re-experiencing mediated this relationship. In line with previous findings, reports of peritraumatic TI were high among PTSD patients. In addition, we showed that it often re-occurred during re-experiencing the traumatic event. The prevalence of TI at different stages post trauma warrants future study.