Both hyper- and hypocortsolism can be associated with stress related illness. The best way to biologically measure stress response is by determining the activity in the HPA axis through levels of cortisol. So far the activity in the HPA axis has been measured in saliva, blood or urine samples. The problem with these measurements is that they only reflect the status at the time of sampling, not retrospectively.
New method can determine cortisol levels three months back.At Linköping university we have developed a method further that can measure concentrations of cortisol retrospectively, about three months backwards in time. (Raul et.al 2004, Clin Biochem). For this measurement we need a three millimeter thick and at least three centimeters long lock of hair, cut as closely to the scalp as possible in the posterior vertex area. Hair grows at about one centimeter a month (Harkey et.al 1993, Forensic Sci), so this gives us a timespan of about three months.
Advantages of the methodTo measure cortisol levels over time allows temporary impact, for example by stress at the time of sampling, variety of circadian rhythms, or the like can be minimized. It is also a non-invasive method that makes it easy to collect samples in large populations and the sampling of children is also easier. Hair has for a long time been used to measure exposure to environmental toxins, medications, drugs or other toxins. Studies show that cortisol levels in hair may be elevated after exposure stress factors such as conditions of employment, unemployment, chronic pain, pregnancy or other major life events. (Sauve 2007, Clin Invest Med,Kalra et.al.2007,Clin Invest Med.Van Uum et.al 2008, Stress, Kirschbaum,2009 Psychoneuroendocrinology)
- Cortisol in hair measured in young adults - a biomarker of major life stressors? Karlén J1, Ludvigsson J, Frostell A, Theodorsson E, Faresjö T. BMC Clin Pathol. 2011
- Higher perceived stress but lower cortisol levels found among young Greek adults living in a stressful social environment in comparison with Swedish young adults. Faresjö Å1, Theodorsson E, Chatziarzenis M, Sapouna V, Claesson HP, Koppner J, Faresjö T. PLoS One. 2013
- Maternal influence on child HPA axis: a prospective study of cortisol levels in hair. Karlén J1, Frostell A, Theodorsson E, Faresjö T, Ludvigsson J. Pediatrics. 2013
- Higher perceived stress and poorer health reflected in elevated cortisol concentrations measured in extracts of hair from middle-aged healthy women Åshild Faresjö *, Miriam Jullander1, Sara Götmalm1 and Elvar Theodorsson. BMC Psychology 2014
- Early psychosocial exposures, hair cortisol levels, and disease risk Karlén, Jerker; Ludvigsson, Johnny; Hedmark, Max; Faresjö, Åshild; Theodorsson, Elvar; Faresjö, Tomas. Pediatrics 2015