Hair cortisol - a potential biological marker for chronic stress

Background At present, salivary cortisol is used as a biomarker of stress, however, due to its large diurnal variation, it can not accurately reflect chronic stress. We hypothesized that cortisol levels measured in hair may correlate better with chronic stress. Methods Hair samples were obtained from 6 healthy adults (3males, 3 females) 6 healthy, term born infants, and 6 infants hospitalized (4 were preterm and two were term), undergoing repeated painful procedures. Demographic data were collected from medical record. Cortisol levels in hair were measured using ELISA with a limit of detection of 0.1nmol/g. Results Hair cortisol levels in the healthy adult females were below the detection limit of the assay. In the healthy males the range of levels was between 0.1 and 0.3nmol/g. Similarly, the healthy infants levels were also below 1.0nmol/g albeit higher than in the adults (range 0.1to 0.8nmol/g). In the hospitalized infants, cortisol levels were greater than 1.0nmol/g in all cases (range 1.4 to 7.6nmol/g). Conclusions These data provide the basis for identifying a potential biomarker for chronic stress in the neonate. It remains to be verified that the same is true in chronic stress in adults. Clinical Pharmacology & Therapeutics (2004) 75, P44–P44; doi: 10.1016/j.clpt.2003.11.166