Acute Dissociation as Part of the Defense Cascade: Associations With Behavioral, Autonomic, and Experiential Threat Responses in Posttraumatic Stress Disorder

Dissociative symptoms, such as depersonalization and derealization, are experienced by about half of individuals with posttraumatic stress disorder (PTSD). Theoretical models propose that acute dissociation is accompanied by specific behavioral, physiological, and experiential alterations and contributes to unfavorable PTSD symptom course. Yet, empirical evidence is scarce. Here, we explored associations between dissociative and behavioral, physiological, and experiential threat responses as well as effects of dissociative responding on PTSD symptom course. Individuals with PTSD (N = 71) participated in a preregistered script-driven imagery study including exposure to standardized, detail-enriched trauma, and neutral scripts. Stabilometry, eye-tracking, facial electromyography, autonomic psychophysiology, and self-report data were collected. Moreover, PTSD symptoms were assessed before and 3 months after testing. Analyses did not link acute dissociation to bodily and facial immobility or staring in response to trauma scripts. However, dissociation displayed an inverted U-shaped relationship with heart rate and was linked to higher nonspecific skin conductance fluctuation and higher high-frequency heart rate variability in response to trauma scripts. Moreover, acute dissociation was linked to higher self-reported negative affect responses to trauma scripts and displayed a U-shaped relationship with unfavorable PTSD symptom course. While results did not confirm hypothesized behavioral markers of dissociation, they do support defense-cascade model assumptions of an inverted U-shaped relationship between dissociation and psychophysiological arousal resulting from a progression of parasympathetic versus sympathetic dominance with increasing dissociation. On an experiential level, results did not confirm posttraumatic dissociation-induced emotional numbing, questioning theoretical notions. The observed nonlinear associations may help explain the heterogeneity of prior findings and might inform an updated conceptualization of posttraumatic dissociation.

Automated summary

This study examined the association between acute dissociation symptoms and behavioral, physiological, and experiential responses in individuals with posttraumatic stress disorder (PTSD), as well as the impact on PTSD symptom course. The results showed that dissociation was related to heart rate, skin conductance fluctuation, and self-reported negative affect responses. Acute dissociation was also associated with an unfavorable PTSD symptom course. However, the hypothesized behavioral markers and emotional numbing were not confirmed. The nonlinear associations observed may help explain the heterogeneity of prior findings and inform an updated conceptualization of posttraumatic dissociation.