Measuring cortisol concentration in hair month-by-month two years retrospectively

Previous studies of cortisol concentrations in hair have concluded that it is not possible to measure more than 6 months retrospectively. This study shows for the first time analyze month-by-month a retrospective period 24 months. In addition, we determined whether concentration decreases with time. The population was 48 women age range 20–51 years, all length cm or longer. participants completed questionnaire examined exposure life stressors and potential confounders. Competitive radioimmunoassay used extract levels hair. overall intraclass correlation substantial (ICC = 0.38, 95% CI 0.29, 0.49), indicating strong within-person during growth period. median were reasonably stable. Wash-out effects small, even those who reported they washed their every day.We conclude detect month at least two years back Changes are likely be related changes due since growth.