Sexual trauma is more strongly associated with tonic immobility than other types of trauma - A population based study.

Background: Tonic immobility is an involuntary motor and vocal inhibition reaction, considered the last-ditch response of the defensive cascade model. It is elicited in context of inescapable threat and perception of entrapment. Our aim was to investigate the association between different traumatic events and peritraumatic tonic immobility (PTI) in a representative sample of the general population.

Methods: This is a cross-sectional study of general population from Rio de Janeiro and São Paulo with 3231 victims of traumatic events aged 15-75 years who completed the Tonic Immobility Scale (TIS). We calculated the frequency of the different traumatic events and estimated the mean scores with 95% confidence intervals for each traumatic event, controlling for the potential confounders using multiple linear regression models. Finally, we calculated the proportion of individual scoring zero in TIS for the 16 traumatic events.

Results: PTI scores in child sexual abuse and adult sexual violence were almost twice as high as in other types of traumatic events, even when controlled for gender and educational level. Torture and war also showed high PTI scores, but these were based on very small number of cases and need to be interpreted with caution. Furthermore, victims of sexual trauma had the lowest proportion of individuals with total absence of PTI symptoms.

Limitations: This is a cross-sectional study and causal inferences must be drawn with caution.

Conclusions: Peritraumatic tonic immobility is more strongly associated with sexual trauma, particularly in childhood, than to other types of trauma in the general population.