Innovations in biological assessments of chronic stress through hair and nail cortisol: Conceptual, developmental, and methodological issues

Abstract

Much of the existing research on biological mechanisms underlying the stress experience has focused largely on moment‐to‐moment stress, rather than on chronic stress, an arguably more powerful predictor of long‐term outcomes. Recent methodological innovations have paved the way for new lines of research on chronic stress, with promising implications for developmental researchers and for those who study health and adversity. In particular, there are increasing studies that have focused on chronic stress assessments by relying on cortisol derived from hair and nails as a biomarker for chronic stress. In this paper, we provide an overview of their use, describe how hair and nail cortisol ought to be conceptualized differently across the lifespan, how developmental factors may impact its interpretation, and the circumstances under which its use may be more methodologically sensible. The purpose of this review is to provoke further discussion and encourage careful research designs that utilize hair and nail cortisol for understanding the effects of chronic stress exposure from the early developmental period, across adverse contexts, and in association with psychological and physical health outcomes.

Associating Emergency Medical Services personnel’s workload, trauma exposure, and health with the cortisol, endocannabinoid, and N-acylethanolamine concentrations in their hair

“…This observation suits previous evidence of higher HCC among individuals with ongoing mental and physiological stress, e.g. industrial shift workers, nursing personnel, or young parents 9 , 10 . Shift work-related disturbances of the sleep rhythm can trigger changes in cortisol metabolism and distribution in the body 5 , 53 , 54 .…”

“…Inconsistent correlations between the concentrations of endocannabinoids and NAEs could indicate that not all these lipids enter the hair through the same pathway 52 . It is important to note that the incorporation of glucocorticoids, endocannabinoids, and NAEs into hair is not yet sufficiently understood 10 , 26 , 28 .…”

“…Moreover, compared to cortisol, relatively little is known about the import kinetics of endocannabinoids and NAEs from the hair follicle into the hair shaft as well as these substances’ temporal deposition in hair 52 . To date, interpreting hair-based biomarkers remains challenging, as the physiological mechanisms of glucocorticoid, endocannabinoid, and NAE incorporation into hair have not yet been sufficiently undersetood 10 , 26 , 28 . Therefore, future research is needed to better characterise the deposition and abundance of lipids and steroids in hair.…”

“…The hypothalamus–pituitary–adrenal (HPA) axis acts as a main regulator of body’s endocrine stress reaction by triggering the release of glucocorticosteroid hormones from the adrenal glands into the blood stream 8 . The glucocorticosteroid hormone cortisol is probably the most intensively investigated bioactive molecule in the context of stress and trauma-associated psychopathology 9 , 10 . During phases of acute and chronic stress, cortisol induces glucose release by glycolysis from the liver to various cells and tissues within minutes and persist over hours 8 .…”

“…In this context, stress research has been focusing on measuring the concentrations of glucocorticoids, endocannabinoids, and NAEs in hair samples. Hair concentrations are considered to retrospectively represent the intra-corporeal activity of measured biomolecules in the course of several weeks to months 10 , 26 – 28 . Such studies provide evidence for altered hair concentrations of cortisol (HCC), endocannabinoids, and NAEs associated with exposure to chronic and traumatic stress as well as related health problems.…”