https://orcid.org/0000-0003-1512-0817
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ABSTRACT
Background: Adequate adaptation of the autonomic nervous system (ANS) is crucial in potentially life-threatening situations. The defence cascade provides a descriptive model of progressing dominant physiological reactions in such situations, including cardiovascular parameters and body mobility. The empirical evidence for this model is scarce, and the influence of physiological reactions in this model for predicting trauma-induced intrusions is unresolved.
Objectives: Using a trauma-film paradigm, we aimed to test physiological reactions to a highly stressful film as an analogue to a traumatic event along the defence cascade model. We also aimed to examine the predictive power of physiological activity for subsequent intrusive symptoms.
Method: Forty-seven healthy female participants watched a stressful and a neutral film in randomized order. Heart rate (HR), heart rate variability (HRV), and body sway were measured. Participants tracked frequency, distress, and quality of subsequent intrusions in a diary for 7 consecutive days.
Results: For the stressful film, we observed an initial decrease in HR, followed by an increase, before the HR stabilized at a high level, which was not found during the neutral film. No differences in HRV were observed between the two films. Body sway and trembling frequency were heightened during the stressful film. Neither HR nor HRV predicted subsequent intrusions, whereas perceived distress during the stressful film did.
Conclusions: Our results suggest that the physiological trauma-analogue response is characterized by an orientation response and subsequent hyperarousal, reaching a high physiological plateau. In contrast to the assumptions of the defence cascade model, the hyperarousal was not followed by downregulation. Potential explanations are discussed. For trauma-associated intrusions in the subsequent week, psychological distress during the film seems to be more important than physiological distress. Understanding the interaction between physiological and psychological responses during threat informs the study of ANS imbalances in mental disorders such as post-traumatic stress disorder.
HIGHLIGHTS
We used a trauma-film analogue to examine the defence cascade model and to investigate the influence of psychophysiological response on subsequent intrusions.
While we found an orientation phase, upregulation phase, and coactivation indicated by heart rate, no downregulation phase was observed.
None of the physiological parameters examined predicted subsequent intrusions, whereas subjective distress during the film did.
Antecedentes: La adaptación adecuada del SNA desempeña un papel crucial en situaciones potencialmente mortales. La cascada de defensa proporciona un modelo descriptivo de las reacciones fisiológicas progresivas y dominantes en tales situaciones, incluidos los parámetros cardiovasculares y la movilidad corporal. La base empírica de este modelo es escasa, y del mismo modo, la influencia de las reacciones fisiológicas dentro de este modelo para predecir intrusiones inducidas por traumas no está resuelta.
Objetivos: Utilizando un paradigma de una película de trauma, nuestro objetivo fue probar la reacción fisiológica a una película altamente estresante, que funciona como análogo a un evento traumático a lo largo del modelo de cascada de defensa. En segundo lugar, nuestro objetivo fue examinar el poder predictivo de la actividad fisiológica para intrusiones posteriores.
Método: 47 participantes femeninas sanas vieron una película estresante y otra neutral en orden aleatorio. Se realizo medición de la frecuencia cardiaca (FC), variabilidad de la frecuencia cardiaca (VFC) y el balanceo corporal. Las participaron registraron la frecuencia, la angustia y la calidad de las intrusiones posteriores en un diario durante 7 días consecutivos.
Resultados: Para la película estresante, observamos una disminución inicial de la FC, seguida de un aumento, antes de que la FC se estabilizara en un nivel alto, lo cual no se encontró durante la película neutra. Para la VFC, no observamos diferencias entre ambas películas. El balanceo del cuerpo y la frecuencia de los temblores aumentaron durante la película estresante. Ni la FC ni VFC, pero sí el malestar percibido durante la película estresante, predijeron intrusiones posteriores.
Conclusión: Nuestros resultados sugieren que la respuesta fisiológica análoga al trauma se caracteriza por una respuesta de orientación y una hiperactivación posterior que alcanza un alto nivel fisiológico. En contraste con los supuestos del modelo de la cascada de defensa, la hiperactivación no fue seguida por una regulación a la baja. Se discuten potenciales explicaciones. Para las intrusiones asociadas al trauma en la semana siguiente, el malestar psicológico durante la película parece ser mas importante que el malestar fisiológico. Comprender la interacción entre las respuestas fisiológicas y psicológicas durante una amenaza informa sobre los desequilibrios del SNA en los trastornos mentales como el trastorno de estrés postraumático.
Acknowledgements
The authors would like to thank Marcel Franz for his help in automating data preprocessing, and Theresa Quaas and Sophie Scharff for their help with study recruitment, conduction, and data transition. The authors also express their gratitude to all women who participated in the study.
Disclosure statement
No potential conflict of interest was reported by the authors.
Data availability
The data that support the findings of this study are openly available in Open Science Framework at https://osf.io/r4g9p/. Please note that five participants decided not to agree to their data being shared publicly; therefore, data for 42 participants are available. With the intention of ensuring privacy rights, we further anonymized the data (see the attached document in the OSF project).
Notes
1 The exploratory hypothesis regarding variety of quality as an outcome variable was added after preregistration. As planned, we assessed different qualities of intrusions using a multiple-choice format. Hence, participants reported multiple qualities for one event, with different qualities over the day. Therefore, we were unable to assign a singular quality type to the subjects, contrary to our best efforts. To test for relationships between physiological parameters and quality components, we implemented the outcome variable ‘variety of intrusions’. This reflects the diversity of perceived qualities during the week but does not set different qualities in a hierarchical order.
2 We changed the preregistered analytical plan. Instead of the preregistered repeated measurements ANOVA with five repetitions (first baseline, 45 s in the middle of the neutral scene, ‘entrance scene’, ‘incipient threat scene’, ‘trapped scene’), the use of timewise analogue sequences for the neutral and the stressful films was deemed more appropriate and caused a 4 (scene) × 2 (condition) design. The power calculation is based on a repeated measurement design with eight repetitions. This is similar but not congruent to a 2 × 4 repeated measurement design, for which the power calculation is more complex and not supported by regular statistical software. Therefore, the above calculated sample size serves as a benchmark. For critical evaluation of the obtained effect sizes, we report confidence intervals (CIs). For the main and interaction analyses we report one-sided 95% CIs for the partial eta square (CIone-sided). Within this approach, the upper CI is fixed to 1.00 to avoid overestimation of the effect size. For subsequent post-hoc comparisons, we used Cohen’s d for pooled repeated measures (Cohen’s dRM, pooled) and related CIs, which takes intercorrelation of the repeated measures into account (Lakens, Citation2013; Lenhard & Lenhard, Citation2016).