How the body’s stress system functions before a traumatic event may help determine who develops persistent post-traumatic stress symptoms afterward, according to a study published in the journal Translational Psychiatry. Researchers have found that childhood adversity, pre-traumatic stress hormone levels, and changes in a small area of the brain called the hypothalamus work together to influence how people respond to trauma.
Although many people experience traumatic events during their lifetime, not everyone develops post-traumatic stress disorder (PTSD). Previous research has shown that adverse childhood experiences, such as abuse, neglect, and family dysfunction, increase the risk of PTSD later in life. Scientists also discovered that childhood adversity can change the body’s stress response systems, including cortisol, the body’s main stress hormone, and the hypothalamus, which helps regulate stress responses. However, until now, researchers did not fully understand how these biological changes interact after a new traumatic event.
Researchers led by Hong Xie of the University of Toledo’s School of Medicine and Life Sciences followed 73 adults who had recently experienced life-threatening trauma. The mean age of the sample was 31 years and included 57 women. Hair samples taken immediately after a traumatic event were used to estimate cortisol levels over the past 1 to 3 months. Within two weeks of the trauma, participants also underwent MRI scans to measure the size of their hypothalamus and completed questionnaires about childhood adversity and post-traumatic stress symptoms. PTSD symptoms were reassessed 3 months later.
Researchers have found that no single biological measurement tells the whole story. Pretrauma cortisol levels or hypothalamic size alone did not consistently predict PTSD symptoms. Rather, a combination of these factors was most important.
Participants who had lower cortisol levels before the trauma, experienced adversity in childhood, and had smaller hypothalamic volumes immediately after the trauma were significantly more likely to experience persistent reexperiencing symptoms. These include intrusive memories and flashbacks three months later. This finding suggests that early life experiences may leave lasting changes in the body’s stress response system that may only become apparent after later trauma.
However, the researchers found that for people with high pre-trauma cortisol levels, there was “no relationship” between childhood adversity and re-experiencing symptoms three months later.
The strongest effects involved the posterior hypothalamus, a part of the brain involved in regulating stress responses and processing emotionally significant memories. The researchers hypothesized that a combination of these factors indicates a blunted and inadequate stress response. These findings may help explain why previous studies that have looked at cortisol or brain structure separately have often yielded inconsistent results.
Xie et al. concluded, “Our findings suggest that interactions between multiple factors, including adverse childhood experiences before the trauma, hair cortisol levels, and the initial structural state of the hypothalamus after trauma, contribute to posttraumatic stress symptoms in the first days and months after adult trauma.”
The researchers note several limitations. For example, this study included a relatively small number of participants and did not include a nontrauma comparison group. Nor could they account for stressful experiences or other mental health disorders in the months leading up to the trauma, or determine when the childhood adversity occurred or how long it lasted.
The research paper, “Pre-traumatic hair cortisol moderates the influence of hypothalamic volume on adverse childhood experiences and adult post-traumatic stress symptoms,” was authored by Hong Xie, Lindsey Davidson, Rowaida M. Hamdan, Chia-Hao Shih, Wei Gao, John T. Wall, Robert E. McCullumsmith, and Xin Wang.
