New Test On Children's Hair May Identify Stress Hormone And Mental Health Risks

Children with chronic illnesses live under a lot of stress, which can increase their risk of depression, anxiety, and behavioral problems. This study followed 244 children for four years and measured cortisol in their hair, a marker of chronic stress. Researchers found that children with consistently high cortisol levels had more psychological problems, while those whose cortisol levels decreased over time had fewer symptoms. This shows that analyzing hair can help identify children at higher risk and guide early care.

Between 15% and 30% of children worldwide live with a chronic physical illness (CPI), such as asthma, juvenile arthritis, type 1 diabetes, or epilepsy. These conditions can significantly limit daily life, bring family concerns, and require difficult treatments.

This combination of factors generates significant stress and increases the risk of mental health problems such as anxiety, depression, or behavioral difficulties. Studies show that up to half of children with chronic physical illnesses develop some type of psychological problem.

When the body experiences stress, it releases a hormone called cortisol. This hormone is produced by a system called the Hypothalamic-Pituitary-Adrenal (HPA) axis. The problem is that when this system is repeatedly activated by constant stress, it can become dysregulated. This means the body can end up releasing too much or too little cortisol.

Research has shown that children with altered cortisol responses are at greater risk of developing psychological problems.

Until recently, cortisol was measured in blood, saliva, or urine, but this only revealed stress levels over the past few hours. To study chronic stress, scientists began using hair. Since hair grows about 1 cm per month, collecting a 3 cm strand can show average cortisol levels accumulated over the past three months. Furthermore, it is a simple and non-invasive method.

Researchers have realized that results on cortisol in hair and mental health in children are still inconclusive: some studies find a positive relationship, others a negative one, and some find no relationship at all. One hypothesis is that different cortisol patterns are linked to different types of symptoms. For example, high cortisol may be linked to symptoms of anxiety and depression (internalizing); and low cortisol may be linked to aggressive behavior or conduct problems (externalizing).

To better understand this, scientists at the University of Waterloo, Canada, analyzed 244 children between the ages of 2 and 16 with chronic illnesses, followed for 48 months in the MY LIFE study in Canada.

• Hair collection: Children provided 3-cm hair samples, which were used to measure average cortisol levels.

• Psychological assessment: Parents completed standardized questionnaires about symptoms of anxiety, depression, and behavior.

• Statistical analysis: Rather than treating all children as if they followed the same pattern, the scientists used a method that looks for subgroups with different cortisol trajectories over time.

The researchers identified three distinct patterns of cortisol levels. These patterns show how each group reacts differently to chronic stress.

The first group, called Hypersecretion, was the largest, comprising approximately 68% of the children. They had consistently high cortisol levels throughout the study period. This pattern suggests that these children were exposed to a continuous state of heightened stress.

The second group, called Hyposecretion, represented 9% of the children. In these children, cortisol levels were persistently low. This pattern may reflect an exhaustion of the stress response system, which stops releasing the hormone in expected amounts.

The third group, called Hyper-to-Hypo, comprised approximately 23% of the children. These children started with high cortisol levels, but over time, these levels decreased. In other words, there was a clear shift in the pattern, moving from excess to lower levels.

When the researchers compared the groups, they noticed something important: children in the Hyper-to-Hypo group showed fewer symptoms of anxiety, depression, and behavioral problems than those in the Hypersecretion group who remained consistently high in cortisol. This finding indicates that decreasing cortisol levels over time may be a sign of healthier adaptation to stress.

The study suggests that chronically high cortisol levels can harm the mental health of children with chronic illnesses. Those whose cortisol levels decreased over time had fewer psychological symptoms. This suggests that hair could be a useful tool for identifying children at higher risk and, in the future, helping doctors offer preventive interventions.

READ MORE:

Association Between Hair Cortisol and Psychopathology in Children With a Chronic Physical Illness

Emma A. L. Littler, Zahid A. Butt, Andrea Gonzalez, and Mark A. Ferro

Stress & Health. Volume 41, Issue 4, August 2025. e70087

https://doi.org/10.1002/smi.70087

Abstract: 

Children with a chronic physical illness (CPI) experience significant stress and are at a greater risk of psychopathology. However, little is known about chronic stress and its relationship with psychopathology in this population. Over the last decade, hair cortisol concentration (HCC) has emerged as a viable biomarker of chronic stress. This study identified trajectories of HCC in children with a CPI and examined their associations with psychopathology. The study included data from 244 children enroled in the Multimorbidity in Children and Youth across the Life-course (MY LIFE) study. MY LIFE is a prospective study of children aged 2–16 years with a CPI recruited from outpatient clinics at a Canadian paediatric hospital and followed for 48 months. Children provided 3-cm hair samples for cortisol assay and parents reported psychopathology symptoms using the Emotional Behavioural Scales. We identified three HCC trajectories: (1) Hypersecretion (n = 166, 68.03%); (2) Hyposecretion (n = 21, 8.61%); and (3) Hyper-to-Hypo (n = 57, 23.36%). When adjusting for sociodemographic and clinical characteristics, children in the Hyper-to-Hypo class had lower internalising (β = −3.17, p = 0.005) and externalising (β = −2.27, p = 0.007) psychopathology symptoms compared to the Hypersecretion class. This study provides evidence that children with a CPI follow distinct HCC trajectories. Children who followed a decreasing trajectory exhibited lower psychopathology symptoms compared to children who followed a consistently elevated trajectory, indicating that chronically high cortisol levels may contribute to the development of psychopathology.