Cortisol in Hair a Marker of Prolonged Stress in Kids

Megan Brooks

October 11, 2013

The level of cortisol in hair may be a marker of prolonged stress in children, which could be a useful "complement" to other ways of studying how stress influences the health of children, report researchers from Sweden.

In a prospective study, Jerker Karlén, MD, and colleagues from Linköping University found a correlation between mother and child hair cortisol levels; high levels of cortisol were related to indicators of psychosocial stress in the child.

"Stress is a major and growing public health problem in most western societies, which also affects children growing up," the authors write.

"Cortisol in hair has the potential of becoming a new indicator for stress exposure over periods of months, and it may be especially useful in stress research among children with the obvious advantage of easy sample collection, being noninvasive, and being independent of stress levels at sample collection," they add.

The study was published online October 7 in Pediatrics.

Lifelong Impact?

The researchers examined cortisol in hair as a potential biomarker of prolonged stress in a subsample of 100 children in the All Babies in Southeast Sweden study. Hair samples were collected prospectively from the children at ages 1, 3, 5, and 8 years and from their mothers during the second and third trimester.

Maternal hair cortisol concentrations during the second and third trimester and child hair cortisol concentrations at ages 1 and 3 years correlated. This finding "suggests a heritable trait or maternal calibration of the child's hypothalamic-pituitary-adrenocortical axis," the researchers note.

The children's hair cortisol levels showed a linear association over time; they gradually decreased and stabilized up to age 8 years. This suggests that the physiologic stress response has "a set point and a stable component and affects the level of cortisol output later in life," the authors write.

Hair cortisol levels in the children were positively correlated with birth weight (P = .020), nonappropriate size (small or large) for gestational age (P = .017), and living in an apartment compared with a house (P = .049), as well as other factors associated with psychosocial stress exposure.

Rich Dataset

Commenting on the findings for Medscape Medical News, Marieke Tollenaar, PhD, assistant professor, Clinical, Health and Neuropsychology Unit, Leiden University, who studies stress and stress hormones but who was not involved in the study, said that at this point, the clinical implications are unclear.

"Individual cortisol values ― derived either from hair or via other techniques ― are still quite hard to interpret, especially as there is a large variability in cortisol levels at a young age. But this method will be directly useful in studies that examine the relation between early life stress and health outcomes, and may also be useful in objectively measuring the outcomes of intervention programs aiming to reduce stress in childhood," she said.

"Hair cortisol is a relatively new way of portraying longer-term cortisol levels, which is thought to reflect stress levels. It is less dependent on momentary cortisol fluctuations, as is common in studies that use saliva or plasma samples," Dr. Tollenaar added.

What is "most noteworthy" about the study, said Dr. Tollenaar, is that the researchers collected these data in young children and were able to prospectively follow them for another 7 years.

"This makes up a very rich dataset, which gives strong reference values for future research using this technique in children."

The authors and Dr. Tollenaar report no relevant financial relationships.

Pediatrics. Published online October 7, 2013. Abstract

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