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

Area of Science:

• Psychology
• Psychiatry
• Trauma Studies

Background:

• Peri-traumatic tonic immobility is linked to post-traumatic stress disorder (PTSD) development and course.
• Persistent tonic immobility in response to trauma reminders can impair functioning and well-being.
• Currently, no validated self-report measures specifically assess post-traumatic tonic immobility.

Purpose of the Study:

• To evaluate the Scale for Tonic immobility Occurring Post-trauma (STOP), a novel self-report measure.
• To assess the presence and severity of tonic immobility responses persisting after trauma exposure.
• To integrate STOP into the assessment of post-traumatic symptomatology.

Main Methods:

• The study involved 462 trauma-exposed participants with a history of tonic immobility.
• Participants completed the STOP, demographic questionnaire, and measures of PTSD, dissociation, anxiety, and depression.
• The Scale for Tonic immobility Occurring Post-trauma (STOP) was evaluated for psychometric properties.

Main Results:

• STOP identified four latent constructs aligned with the human defense cascade model.
• The scale captures sensorimotor, perceptual, and dissociative alterations associated with post-traumatic tonic immobility.
• STOP demonstrated excellent reliability and good construct/convergent validity with PTSD and dissociation measures.
• Findings suggest tonic immobility is closely related to dissociative post-traumatic symptomatology.

Conclusions:

• The STOP scale shows excellent preliminary psychometric properties.
• It may be a valuable tool for researchers and clinicians.
• The scale can be used to assess chronic tonic immobility in diverse trauma-exposed populations.