New research released by the University of Oklahoma using data gathered seven years after the Oklahoma City bombing suggests survivors carry physiological traces of their trauma.
OU's study explores biological stress measures among 60 heavily impacted direct survivors compared to a local control group who were not affected by the bombing. Both groups were pre-selected to be healthy, and survivors had a mean age of 47 years, while comparison participants had a mean age of 42.
Dr. Phebe Tucker, the study's lead author and professor emeritus of psychiatry at the OU College of Medicine, said survivors were selected from an Oklahoma State Department of Health registry. Non-exposed control participants were recruited via flyers and word of mouth.
"We are forever grateful to these people who determined early on that they would participate in research because they felt it was important for us to understand how research affected them and might affect other people as well," Tucker said.
Tucker said there have been previous studies examining biological stress and psychological symptoms in terrorism survivors. But this research is thought to be the first of its kind to study three different biological systems among healthy people who survived the same traumatic event. Those include the following:
- Cortisol: A steroid hormone that helps regulate the body's response to stress. High and low levels can impact a person's health.
- Interleukins: Inflammatory substances that play a role in the body's immune system.
- Heart rate and blood pressure.
Tucker said it also covered emotional stress measures, and researchers found survivors' PTSD and depression scores were not elevated and did not correlate with stress biomarkers. The study suggests their bodies remembered the trauma they experienced.
"It was as if the mind was kind of letting go of some of the stress in these healthy people, but the body had not forgotten," Tucker said.
Survivors, for example, had lower morning salivary cortisol than the control participants. Tucker said this is interesting because cortisol levels are usually higher in the morning.
"It just depends on how long after the trauma [research is done]. And so these people, for the most part, did not have PTSD. So chronic PTSD, in many studies, has been shown to have lower cortisol levels," Tucker said. "So even though these folks didn't have PTSD, they were sort of consistent with some of that research."
Survivors were also found to have higher blood pressure but a lower heart rate in response to trauma cues.
"Usually it's elevated, and so we did not find that it was elevated like we thought it would be. So I think the reason would be — that it didn't increase to a great degree – because of the blunted response," Tucker said. "It was already high to start with, so it couldn't jump up even higher."
Finally, Tucker said interleukin 1B, which is linked with inflammation, was significantly higher in survivors, and interleukin 2R, which has a protective role, was lower. Tucker said although the group studied was considered healthy, Interleukin 1B is typically seen in people with illnesses and inflammation.
"What we saw was consistent with an inflammation trauma response," Tucker said.
Tucker said she left the study with questions, like if these findings meant participants' bodies are preparing them for future stress, or if these lasting stress biomarkers might lead to long-term health effects.
"There are many effects of trauma. We think about physical injuries, and we think about the emotional stress, and those can linger on. But we don't think, necessarily, about those hidden biological stress markers that are below the surface. What are they doing, and how important is that?" Tucker said. "... I think we need more research on that."
