An Ambulatory Investigation of Momentary Interoception and PTSD Symptoms

Abstract


Background: Interoception, the perception of internal bodily states and sensations, is believed to be negatively impacted by trauma. There are unique bodily responses that occur because of trauma (e.g., increased heartrate during sexual assault) that can subsequently make these sensations, and the body itself, an egregious trauma reminder that is avoided or hypersurveilled. Bodily sensations, and attention to them, are part of some posttraumatic stress disorder (PTSD) symptom clusters, namely hypervigilance, exaggerated startle, flashbacks, and dissociation. Existing theories that hypothesize that interoception is stronger during moments of hyperarousal and weaker during moments of dissociation are built on the assumption that both interoception and PTSD symptoms are dynamic, changing experiences that occur within people over time. Yet, there are only a few studies empirically testing these hypotheses, none of which have used ambulatory or within-subjects designs. Thus, the proposed study developed a novel measure of interoception to examine the associations between momentary interoception and four PTSD symptoms as they occur in daily life: hypervigilance, exaggerated startle, dissociation, and flashbacks.

Method: A total of 80 trauma-exposed individuals from the community completed ambulatory assessments up to 17 times per day for 3 days while simultaneously wearing a psychophysiological device tracking their interbeat intervals (IBI; i.e., time between each heartbeat). Interoception was measured by examining the association between IBI and self-reported physical sensations in the body. The CAPS-5 was administered to obtain a measure of PTSD symptom severity to include as a covariate. Multilevel models were tested to examine whether momentary PTSD symptoms moderated the effect of IBI on physical sensations while covarying for overall PTSD symptom severity.

Results: Multilevel modeling results indicated that only 34% of variability of self-reported physical sensations could be attributed to between-subjects differences. IBI significantly predicted physical sensations (B = -0.07, SE = 0.03, p = .010). There was no interaction between IBI and hypervigilance (B = -0.04, SE = 0.05, p = .442), exaggerated startle (B = -0.04, SE = 0.06, p = .475), or dissociation (B = 0.02, SE = 0.17, p = .886); however, there was a significant IBI X flashback interaction, indicating interoception was stronger during flashbacks. There was also a three-way interaction between IBI, dissociation, and PTSD symptom severity, such that interoception was stronger during moments with greater dissociation severity, but only for people with high overall PTSD symptom severity.

Discussion: Results largely contradicted past theories about the hypothesized associations between interoception and PTSD symptom clusters. Interoception was unrelated to hypervigilance and exaggerated startle but was stronger during flashbacks. Interoception was stronger as dissociation increased, but only among those with high overall PTSD symptoms severity, contradicting hypotheses. Clinicians should be aware that trauma survivors’ ability to notice bodily sensations may be impacted by some PTSD symptoms on a moment-to-moment basis. Findings from the study provide support for calls to integrate somatic and body-oriented work into trauma treatment which could in turn improve one’s groundedness and ability detect sensations in the body.