Assessing Post-Traumatic Tonic Immobility Responses: The Scale for Tonic Immobility Occurring Post-Trauma

Abstract

Background: Peri-traumatic tonic immobility has been associated with the development and course of post-traumatic stress disorder. Despite serving as an adaptive late-stage defense response, tonic immobility that continues in response to posttraumatic reminders may lead to reduced functioning and a diminished sense of well-being. At present, no validated selfreport measures assess post-traumatic tonic immobility responses specifically. Methods: The primary objective of the present study was to evaluate the Scale for Tonic immobility Occurring Post-trauma (STOP), the first self-report measure developed to assess for the presence and severity of tonic immobility responses that persist following trauma exposure as part of post-traumatic symptomatology. Trauma-exposed clinical and non-clinical participants (N ¼ 462) with a history of tonic immobility completed a demographic questionnaire, the STOP, and measures of post-traumatic symptoms, dissociation, anxiety, and depression. Results: STOP assessed four latent constructs, which were interpreted following the human defense cascade model. Together, these factors capture the sensorimotor and perceptual alterations, and dissociative experiences, associated with post-traumatic tonic immobility as a trauma-related altered state. Residual symptoms and the experience of negative affect following this response (including guilt and shame) are also represented. STOP scores demonstrated excellent reliability, as well as good construct and convergent validity, with other measures of dissociation and post-traumatic stress disorder. Results from the present study suggest tonic immobility is most consistent with other dissociative post-traumatic symptomatology. Conclusions: STOP demonstrates excellent preliminary psychometric properties and may be useful for researchers and clinicians wishing to assess chronic forms of tonic immobility across trauma-exposed, clinical and community samples.

Maladaptive Alterations of Defensive Response Following Developmental Complex Stress in Rats

“…These results may also be linked to previous work comparing dissociation in a clinical population who were sexually assaulted and TI in animals [54][55][56]. Because TI is especially associated with failure of integrating information and reacting appropriately and loss of chance to avoid further damage, TI can lead ComS group accident-proneness [57][58][59].…”

"I just became like a log of wood … I was paralyzed all over my body": women's lived experiences of tonic immobility following rape

“…The experiences of raped women hinting TI as mental paralysis is another theme derived from the stories of half of the participants in this study and which is consistently reported in both male and female rape victims researchers ( Duma, 2016a ; Littleton et al., 2020 ; Lloyd et al., 2019 ; Mgolozeli and Duma, 2020a ; Moller et al., 2017 ). Mental paralysis as a manifestation linked to TI, is thought to be an advantage and a protective mechanism for the victims of rape because the rapist may assume that an immobile victim showing mental paralysis is ‘dead’ and thus, physical harm to the victim is reduced ( Rütting et al., 2007 ; Van Buren and Weierich, 2015 ).…”

“…Others have doubted the presence of any changes in heartrate as traumatic response during TI. They assert that the features of TI are either not clear, often inconsistent or difficult to differentiate from those of ‘freezing’ during the state of shock ( Hagenaars et al., 2014 ; Lloyd et al., 2019 ). Overall, nearly half of the participants narrated the experience of TI as an altered physical state.…”

“…This necessitates further research; since TI is an emerging area of research and more African studies are needed to make definite contextual conclusions. For instance, even though western scientists argue about the occurrence of either rapid or slow heartbeats among victims during incidences of rape ( Kozlowska et al., 2015 ; Volchan et al., 2017 ), other scientists doubt if there are any heart rate changes at all ( Hagenaars et al., 2014 ; Lloyd et al., 2019 ). In this study though, participants narrated the experience of rapid heart rates (Ifeoma 23; Farida; 18; Rejoice 31), yet this cannot be deemed conclusive.…”

Pedunculopontine-induced cortical decoupling as the neurophysiological locus of dissociation.

“…Given these findings, excessive REM sleep drive could explain the experiences of detachment associated with some cases of posttraumatic stress (Steuwe, Lanius, & Frewen, 2012). Also, some adherents of the TM maintain that dissociation is a manifestation of something akin to tonic immobility (Lloyd, Lanius, Brown, Neufeld, Frewen, & McKinnon, 2019). Although this is link is speculative, a large set of behavioral and physiological commonalities has inspired the hypothesis that there is an evolutionary kinship between tonic immobility and REM sleep (Tsoukalas, 2012).…”