Associations between Allostatic Load and Post-Traumatic Stress Disorder: A Scoping Review

Background: Experiencing traumatic events that lead to the development of post-traumatic stress disorder (PTSD) or PTSD symptomology can negatively affect health outcomes. In the United States, it is estimated that 80% of individuals will experience at least one lifetime traumatic event. Of those who experience traumatic events, the lifetime prevalence of PTSD is estimated to range from 6%-10% in the general population and cooccurs in 20%-47% of persons with serious mental illness. Given the prevalence of PTSD and its association with other behavioral and chronic physical health outcomes, it is necessary to better understand the etiology of the disorder. Allostatic load, which represents the cumulative biological wear and tear of exposure to stress, can be employed to better understand the physiological etiology of PTSD. However, the association of allostatic load with PTSD has been largely unexplored.

Method: This scoping review was informed by PRISMA Extension for Scoping Review guidelines. The following databases were searched: PubMED, PsycINFO, Academic Search Complete, MEDLINE, Social Work Abstracts, Sociological Abstracts, Social Service Abstracts, and the Published International Literature on Traumatic Stress (PILOTS). We included both published and un-published empirical studies on PTSD or PTSD symptomology that employed the theory of allostatic load and assessed allostatic load through a cumulative measure of biological risk. Two reviewers independently screened studies for inclusion and extracted data. Discrepancies were resolved through consensus. Items extracted included study and participant characteristics and outcomes related to the operationalization of allostatic load and its association with PTSD. Results were summarized narratively and in tabular form.

Results: Of the initial 111 studies identified through the database searches, only four met inclusion criteria. Studies range between 81 to 197 participants who were primarily female; two studies focused specifically on minority physical and mental health. Nineteen different biomarkers were used to assess allostatic load, with 7 to 13 biomarkers used in each study. Findings were mixed as to the association between allostatic load and PTSD. Allostatic load was positively associated with PTSD diagnosis; however, studies measuring only PTSD symptomatology found no relationship between PTSD symptoms and allostatic load. Additionally, heterogeneity was present in the operationalization of allostatic load.

Discussion: Allostatic load is a useful theoretical framework for explicating the biological etiology of stress-related physical and mental health disorders. To date, few PTSD researchers have applied this theoretical framework to their research. Among those who have, studies show that allostatic load can be a beneficial tool for understanding the biological changes associated with PTSD. Moving forward, additional research should focus on standardizing measures and identifying potential confounders. For healthcare providers, allostatic load may clarify the comorbidity of PTSD with chronic health conditions, and underscores the need to implement models of integrated healthcare, both in primary care and mental health settings due to the high proportion of PTSD and physical health conditions among persons with schizophrenia spectrum, bipolar, and major depressive disorders. A better understanding of the physiological changes associated with PTSD can in turn lead to more effective prevention and treatment efforts.